System and method for testing network attack protection capability of battery system and electronic equipment

Abstract

The invention relates to the technical field of battery protection testing, and provides a battery system network attack protection capability testing system and method and electronic equipment, and the testing system comprises a battery simulation unit, an energy controller, an instruction generation unit and an instruction inspection unit. The battery simulation unit simulates battery physical characteristics in real time and outputs battery simulation parameters; the instruction generation unit generates and sends a scheduling control instruction according to the battery simulation parameters; the energy controller is used for detecting and shielding a malicious control instruction and sending out an alarm; the instruction inspection unit is respectively connected with the energy controller and the battery simulation unit in series, and is used for acquiring a scheduling control instruction, performing safety inspection in combination with current battery simulation parameters, and judging the system protection capability; if the malicious control instruction is detected, judging that the protection test is not passed; and if only the normal scheduling instruction is detected, judging that the protection test passes, recording the normal scheduling instruction and resetting the test. The battery system protection capability testing device has a good battery system protection capability testing effect.

Description

Technical Field

[0001] This invention relates to the field of battery protection testing technology, and in particular to a battery system network attack protection capability testing system, method, electronic device, and computer-readable storage medium. Background Technology

[0002] In the digital age, connecting energy storage stations, charging piles, and other new energy infrastructure to the internet for management is an indispensable operational method. However, while these technologies are developing rapidly, they also introduce new cybersecurity issues. For example, compared to gasoline vehicles and battery systems, highly integrated and intelligent electric vehicles, battery management systems, and energy storage stations are more vulnerable to cyberattacks. Furthermore, for ordinary information systems, the main losses after a malicious cyberattack are the loss of data and information system availability or the leakage of privacy and secrets. Since battery-equipped devices are connected to high-voltage electrical systems, attacks on their controllers, management systems, and other components could potentially lead to battery fires and explosions, endangering lives and causing extremely serious consequences.

[0003] Existing technical solutions simply combine common network information system security technologies and apply them to specific energy scenarios, without customizing protection solutions for the characteristics of new energy scenarios such as energy storage stations and charging piles. Currently, a better protection method is to enhance security by using two computing units to specifically protect the battery system: the first computing unit performs security audits on scheduling and control commands, which can reject malicious accusation commands that could cause destructive attacks if the cloud platform is controlled by an attacker; even if an attacker has breached the battery security system, because the first computing module and the second computing unit are managed separately, the first computing unit module operates independently, and the attacker cannot affect it; the first computing unit only checks whether the control operation is destructive in the current environment, without performing other operations or interfering with normal management and control.

[0004] Therefore, from the user's perspective, there is a need for methods and systems to test whether the purchased new energy equipment has the ability to protect against malicious attacks that could compromise battery safety. However, the aforementioned battery protection system cannot be used to test the performance of new energy equipment in terms of its ability to protect against malicious attacks that could compromise battery safety. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention proposes a battery system network attack protection capability testing system to solve the problem that existing battery protection systems cannot be used to test whether new energy devices have the ability to protect against malicious attacks against batteries.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: In a first aspect, embodiments of the present invention provide a battery system network attack protection capability testing system, the testing system comprising a battery simulation unit, an energy controller, an instruction generation unit, and an instruction verification unit; The battery simulation unit is deployed at the end of the system and is used to simulate the physical characteristics of the battery in real time and output battery simulation parameters. The battery simulation parameters are sent to the command generation unit via the command detection unit and the energy controller. The instruction generation unit is integrated into the energy controller or connected in series as a separate device at the front end of the energy controller; the instruction generation unit is used to acquire the battery simulation parameters, and generate and send scheduling control instructions based on the battery simulation parameters; wherein, the scheduling control instructions include normal scheduling instructions and malicious control instructions; The energy controller is used to detect and block the malicious control commands and issue a warning. The instruction verification unit is serially connected to both the energy controller and the battery simulation unit. It is used to collect the scheduling control instructions and, in conjunction with the current battery simulation parameters, perform a security review to determine the system's protection capabilities. If the malicious control command is detected, the protection test is deemed to have failed. If only the normal scheduling instruction is detected, the protection test is deemed to have passed, and the normal scheduling instruction is recorded and the test is reset.

[0007] Preferably, the battery simulation parameters include at least one of the following: cell voltage, cell current, cell temperature, battery state of charge, battery state of health, maximum voltage, minimum voltage, and maximum voltage difference.

[0008] Preferably, the instruction generation unit is further configured to: randomly switch to normal mode or attack test mode based on the real-time status of the battery simulation unit; send the normal scheduling instruction in the normal mode; and send the malicious control instruction in the attack simulation mode.

[0009] Preferably, the battery system network attack protection capability testing system further includes a monitoring device and a converter; the monitoring device, the converter, and the battery simulation unit are connected via a bus communication connection. The monitoring equipment is used to monitor the status of the battery simulation unit in real time. The converter is used to execute corresponding operations according to the received scheduling control instructions, and to feed back the status of the corresponding operations in real time through the bus, and cyclically send the feedback to the battery simulation unit for testing.

[0010] Secondly, an embodiment of the present invention provides a method for testing the network attack protection capability of a battery system. The method is based on the battery system network attack protection capability testing system described above, and includes the following steps: Step S1: Simulate the physical characteristics of the battery in real time through the battery simulation unit and output the battery simulation parameters. Send the battery simulation parameters to the command generation unit through the command detection unit and the energy controller. Step S2: Obtain the battery simulation parameters through the instruction generation unit, and generate and send scheduling control instructions based on the battery simulation parameters; wherein, the scheduling control instructions include normal scheduling instructions and malicious control instructions; Step S3: Use the energy controller to block the malicious control command and issue a warning; Step S4: The scheduling control command is collected in real time by the command verification unit, and a security review is performed in combination with the current battery simulation parameters to determine the system's protection capability; If the malicious control command is detected, the protection test is deemed to have failed. If only the normal scheduling instruction is detected, the protection test is deemed to have passed, and the normal scheduling instruction is recorded and the test is reset.

[0011] Preferably, the battery simulation parameters include at least one of the following: cell voltage, cell current, cell temperature, battery state of charge, battery state of health, maximum voltage, minimum voltage, and maximum voltage difference.

[0012] Preferably, step S2 further includes the following sub-steps: Based on the real-time status of the battery simulation unit, it is randomly positioned in either normal mode or attack test mode; in normal mode, the normal scheduling command is sent; in attack simulation mode, the malicious control command is sent.

[0013] Thirdly, embodiments of the present invention also provide an electronic device, the electronic device including a processor and a memory, the memory storing a computer program executable by the processor, and the processor executing the steps in the battery system network attack protection capability testing method described above when reading the computer program in the memory.

[0014] Fourthly, embodiments of the present invention also provide a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps in any of the above-described battery system network attack protection capability testing methods.

[0015] Compared with related technologies, in the embodiments of the present invention, the battery simulation unit simulates the physical characteristics of the battery in real time and outputs battery simulation parameters. The battery simulation parameters are then sent to the instruction generation unit via the instruction detection unit and the energy controller. The instruction generation unit is used to acquire the battery simulation parameters and generate and send scheduling control instructions based on the battery simulation parameters. The energy controller is used to block malicious control instructions and issue warnings. The instruction verification unit is serially connected to the energy controller and the battery simulation unit, respectively, and is used to collect scheduling control instructions and perform security reviews based on the current battery simulation parameters to determine the system's protection capabilities. If a malicious control instruction is detected, the protection test is deemed to have failed. If only the normal scheduling instructions are detected, the protection test is deemed to have passed, and the normal scheduling instructions are recorded and the test is reset. This facilitates the verification of whether energy storage systems, charging piles, and other equipment have the ability to protect against malicious attacks targeting batteries, resulting in good test performance. Attached Figure Description

[0016] The present invention will now be described in detail with reference to the accompanying drawings. The above and other aspects of the present invention will become clearer and more readily understood through the detailed description following the accompanying drawings. In the drawings: Figure 1 This is a block diagram of the battery system network attack protection capability testing system provided in Embodiment 1 of the present invention; Figure 2 This is a flowchart of a battery system network attack protection capability testing method provided in Embodiment 2 of the present invention; Figure 3 This is a module diagram of an electronic device provided in Embodiment 3 of the present invention. Detailed Implementation

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0018] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 Please see Figure 1 As shown, this embodiment of the invention provides a battery system network attack protection capability testing system 200, which includes a battery simulation unit 21, an energy controller 23, an instruction generation unit 24, and an instruction verification unit 22.

[0021] The battery simulation unit 21 is deployed at the end of the system and is used to simulate the physical characteristics of the battery in real time and output battery simulation parameters. The battery simulation parameters are sent to the instruction generation unit 24 via the instruction detection unit and the energy controller 23.

[0022] The instruction generation unit 24 is integrated into the energy controller 23 or connected in series as a separate device at the front end of the energy controller 23; the instruction generation unit 24 is used to obtain the battery simulation parameters and generate and send scheduling control instructions based on the battery simulation parameters; wherein, the scheduling control instructions include normal scheduling instructions and malicious control instructions.

[0023] Specifically, the instruction generation unit 24 calculates the scheduling instruction range for normal mode and attack mode based on the received parameters. For example, the normal mode scheduling instruction range is "0xx3-0xx9", and the malicious control instruction range for attack mode is "0xx1-0xx2". It then randomly sends normal scheduling instructions and malicious control instructions to the Ethernet. Normal mode scheduling instructions: all instructions conforming to the format 0xx3 to 0xx9 (where xx is any two legal characters). Attack mode malicious instructions: instructions conforming to the format 0xx1 to 0xx2 (last digit is 1 or 2).

[0024] The energy controller 23 is used to detect and block malicious control commands and issue warnings. The energy controller 23 is connected to the command generation unit 24 via Ethernet communication. By installing Ethernet inside the energy controller 23 and the command generation unit 24, it is responsible for converting the device's digital signals into electrical (or optical) signals suitable for Ethernet transmission and for enabling data transmission and reception.

[0025] The instruction verification unit 22 is serially connected to both the energy controller 23 and the battery simulation unit 21. It is used to collect the scheduling control instructions and perform a security review based on the current battery simulation parameters to determine the system's protection capabilities. If the actual equipment cannot meet the serial connection requirements, the instruction verification unit 22 can also be mounted on a bus to acquire all information on the bus.

[0026] If the malicious control command is detected, the protection test is deemed to have failed. If only the normal scheduling instruction is detected, the protection test is deemed to have passed, and the normal scheduling instruction is recorded and the test is reset.

[0027] Specifically, the battery simulation unit 21 simulates the physical characteristics of the battery in real time and outputs battery simulation parameters. These parameters are then sent to the command generation unit 24 via the command detection unit and the energy controller 23. The command generation unit 24 acquires the battery simulation parameters and generates and sends scheduling control commands based on them. The energy controller 23 blocks malicious control commands and issues warnings. The command verification unit 22 is communicatively connected to both the command generation unit 24 and the battery simulation unit 21. It collects scheduling control commands and performs a security review based on the current battery simulation parameters to determine the system's protection capabilities. If a malicious control command is detected, the protection test fails. If only the normal scheduling command is detected, the protection test passes, the normal scheduling command is recorded, and the test is reset. This facilitates the verification of whether energy storage systems, charging piles, and other equipment have the ability to protect against malicious attacks targeting batteries, resulting in good test performance.

[0028] In this embodiment, the battery simulation parameters include at least one of the following: cell voltage, cell current, cell temperature, state of charge (SOC), state of health (SOH), maximum voltage, minimum voltage, and maximum voltage difference. Cell voltage directly reflects the cell's charge / discharge state: excessively high voltage (e.g., exceeding 4.3V) may lead to overcharging risk, while excessively low voltage (e.g., below 2.5V) may cause over-discharge damage. Cell voltage is also used to determine cell balance: excessive differences in cell voltage can affect the overall performance of the battery pack, requiring balancing control through a battery management system (BMS).

[0029] Individual cell current is used to monitor charge and discharge rates: excessive current (such as exceeding the cell's rated charge and discharge rate) can lead to increased heat generation, reduced lifespan, and even safety hazards. It calculates the cell's real-time power (voltage × current) and energy changes, aiding in the calculation of state of charge (SOC).

[0030] Cell temperature primarily affects battery performance and safety: low temperatures (e.g., <0℃) lead to decreased charging efficiency and capacity decay; high temperatures (e.g., >50℃) accelerate electrolyte decomposition and increase the risk of thermal runaway. It is also used in thermal management systems (TMS) for control, such as activating cooling fans or heating films to maintain the temperature within an ideal range (e.g., 25℃~40℃).

[0031] SOC (State of Charge) represents the percentage of a battery's remaining charge relative to its rated capacity. SOH (State of Health) is used to assess battery life: when SOH is below 70%~80%, the battery is generally considered to be entering the retirement stage (the threshold varies depending on the application). Predicting maintenance needs: A decrease in SOH can provide early warning of battery performance degradation, assisting in the development of replacement or repair plans.

[0032] Maximum voltage is used to prevent overcharging: when the voltage of a single cell approaches or exceeds the charging cutoff voltage (e.g., 4.2V for lithium-ion batteries), charging must be stopped immediately or equalization must be initiated. Monitoring consistency: compared with the minimum voltage, it reflects the degree of dispersion between cells.

[0033] Minimum voltage is used to prevent over-discharge: When the voltage of a single cell falls below the discharge cutoff voltage (e.g., 2.8V for lithium-ion batteries), discharge must be stopped to protect the cell. Identifying lagging cells: Cells with persistently low voltage may have internal short circuits or severe aging issues and require thorough investigation.

[0034] The maximum voltage difference is the difference between the "maximum voltage" and the "minimum voltage" in the battery pack, reflecting the voltage balance between the cells.

[0035] Specifically, the battery simulation unit 21 sends data such as the single cell voltage, single cell current, single cell temperature, SOC, SOH, maximum voltage, minimum voltage, and maximum voltage difference of the simulated battery to the bus, and then sends them to the energy controller 23 instruction generation unit 24 in the Ethernet via the instruction verification unit 22 and the energy storage unit-level energy controller 23.

[0036] In this embodiment, the instruction generation unit 24 is further configured to: randomly enter a normal mode or an attack test mode based on the real-time status of the battery simulation unit 21; send the normal scheduling instruction in the normal mode; and send the malicious control instruction in the attack simulation mode.

[0037] In this embodiment, the battery system network attack protection capability testing system further includes a monitoring device 26 and a converter 25; the monitoring device 26, the converter 25 and the battery simulation unit 21 are connected via bus communication.

[0038] The monitoring device 26 is used to monitor the status of the battery simulation unit 21 in real time. Optionally, the monitoring device 26 can be a camera, webcam, etc.

[0039] The converter 25 is used to execute corresponding operations according to the received scheduling control instructions, and to feed back the status of the corresponding operations in real time through the bus, and cyclically send the feedback to the battery simulation unit 21 for testing.

[0040] In this embodiment, the instruction verification unit 22 can also be combined with the battery simulation unit 21, or other modules can be added, and there are various ways to implement it.

[0041] Example 2 Please see Figure 2 As shown in the figure, an embodiment of the present invention provides a method for testing the network attack protection capability of a battery system. The testing method is implemented based on the battery system network attack protection capability testing system 200 described above, and the testing method includes the following steps: Step S1: Simulate the physical characteristics of the battery in real time through the battery simulation unit 21 and output the battery simulation parameters. Send the battery simulation parameters to the instruction generation unit 24 through the instruction detection unit and the energy controller 23. Step S2: Obtain the battery simulation parameters through the instruction generation unit 24, and generate and send scheduling control instructions based on the battery simulation parameters; wherein, the scheduling control instructions include normal scheduling instructions and malicious control instructions; Step S3: Use the energy controller 23 to block the malicious control command and issue a warning; Step S4: The scheduling control command is collected in real time by the command verification unit 22, and a safety review is performed in combination with the current battery simulation parameters to determine the system's protection capability; If the malicious control command is detected, the protection test is deemed to have failed. If only the normal scheduling command is detected, the protection test is considered passed, and the normal scheduling command is recorded and the test is reset. This facilitates the verification of whether energy storage systems, charging piles, and other equipment have the ability to protect against malicious attacks targeting batteries, resulting in good test results.

[0042] In this embodiment, the simulated battery parameters include at least one of the following: cell voltage, cell current, cell temperature, battery state of charge, battery state of health, maximum voltage, minimum voltage, and maximum voltage difference. Cell voltage directly reflects the cell's charge / discharge state: excessively high voltage (e.g., exceeding 4.3V) may lead to overcharging risk, while excessively low voltage (e.g., below 2.5V) may cause over-discharge damage. Cell voltage is also used to determine cell balance: excessive differences in cell voltage can affect the overall performance of the battery pack, requiring balancing control through a battery management system (BMS).

[0043] In this embodiment, step S2 further includes the following sub-steps: Based on the real-time status of the battery simulation unit 21, it randomly enters either normal mode or attack test mode; in normal mode, it sends the normal scheduling command; in attack simulation mode, it sends the malicious control command.

[0044] In this embodiment, the instruction generation unit 24 is deployed in the energy storage unit-level energy controller 23 in software form, and the principle and working steps are S1-S4. This simplifies the testing equipment and eliminates the need to deploy a station-level energy control unit.

[0045] The battery system network attack protection capability testing method in this second embodiment has the same technical effect as that in the first embodiment, and will not be described again here.

[0046] Example 3 Please see Figure 3 As shown, this embodiment of the invention also provides an electronic device 300, which includes a processor 301 and a memory 302. The memory 302 stores a computer program that can be executed by the processor 301. When the processor 301 reads the computer program in the memory 302, it executes the steps in the battery system network attack protection capability testing method described above.

[0047] Step S1: Simulate the physical characteristics of the battery in real time through the battery simulation unit 21 and output the battery simulation parameters. Send the battery simulation parameters to the instruction generation unit 24 through the instruction detection unit and the energy controller 23. Step S2: Obtain the battery simulation parameters through the instruction generation unit 24, and generate and send scheduling control instructions based on the battery simulation parameters; wherein, the scheduling control instructions include normal scheduling instructions and malicious control instructions; Step S3: Detect and block the malicious control command using the energy controller 23 and issue a warning; Step S4: The scheduling control command is collected in real time by the command verification unit 22, and a security review is performed in conjunction with the current battery simulation parameters to determine the system's protection capability. If the malicious control command is detected, the protection test is deemed to have failed. If only the normal scheduling instruction is detected, the protection test is deemed to have passed, and the normal scheduling instruction is recorded and the test is reset.

[0048] Example 4 This invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps in any of the above-described battery system network attack protection capability testing methods.

[0049] Those skilled in the art will understand that all or part of the processes in the methods for implementing the electronic devices of the embodiments can be implemented by instructing related hardware through a computer program. This program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0050] It should be noted that the various embodiments described above with reference to the accompanying drawings are merely illustrative of the present invention and not intended to limit its scope. Those skilled in the art should understand that any modifications or equivalent substitutions made to the present invention without departing from its spirit and scope should be included within the scope of the present invention. Furthermore, unless the context otherwise requires, words appearing in the singular include those in the plural, and vice versa. Additionally, unless specifically stated otherwise, all or part of any embodiment may be used in conjunction with all or part of any other embodiment.

Claims

1. A battery system network attack protection capability testing system, characterized in that, The testing system includes a battery simulation unit, an energy controller, an instruction generation unit, and an instruction verification unit. The battery simulation unit is deployed at the end of the system and is used to simulate the physical characteristics of the battery in real time and output battery simulation parameters. The battery simulation parameters are sent to the command generation unit via the command detection unit and the energy controller. The instruction generation unit is integrated into the energy controller or connected in series as a separate device at the front end of the energy controller; the instruction generation unit is used to acquire the battery simulation parameters, and generate and send scheduling control instructions based on the battery simulation parameters; wherein, the scheduling control instructions include normal scheduling instructions and malicious control instructions; The energy controller is used to detect and block the malicious control commands and issue a warning. The instruction verification unit is serially connected to both the energy controller and the battery simulation unit. It is used to collect the scheduling control instructions and, in conjunction with the current battery simulation parameters, perform a security review to determine the system's protection capabilities. If the malicious control command is detected, the protection test is deemed to have failed. If only the normal scheduling instruction is detected, the protection test is deemed to have passed, and the normal scheduling instruction is recorded and the test is reset.

2. The battery system network attack protection capability testing system according to claim 1, characterized in that, The battery simulation parameters include at least one of the following: cell voltage, cell current, cell temperature, battery state of charge, battery state of health, maximum voltage, minimum voltage, and maximum voltage difference.

3. The battery system network attack protection capability testing system according to claim 1, characterized in that, The instruction generation unit is further configured to: randomly switch to normal mode or attack test mode based on the real-time status of the battery simulation unit; send the normal scheduling instruction in the normal mode; and send the malicious control instruction in the attack simulation mode.

4. The battery system network attack protection capability testing system according to claim 1, characterized in that, The battery system network attack protection capability testing system also includes monitoring equipment and a converter; the monitoring equipment, the converter, and the battery simulation unit are connected via bus communication. The monitoring equipment is used to monitor the status of the battery simulation unit in real time. The converter is used to perform corresponding operations according to the received scheduling control instructions, and to feed back the status of the corresponding operations in real time through the bus, and to cycle through the battery simulation unit for testing.

5. A method for testing the network attack protection capability of a battery system, said testing method being implemented based on the battery system network attack protection capability testing system as described in any one of claims 1-4, characterized in that, The testing method includes the following steps: Step S1: Simulate the physical characteristics of the battery in real time through the battery simulation unit and output the battery simulation parameters. Send the battery simulation parameters to the command generation unit through the command detection unit and the energy controller. Step S2: Obtain the battery simulation parameters through the instruction generation unit, and generate and send scheduling control instructions based on the battery simulation parameters; wherein, the scheduling control instructions include normal scheduling instructions and malicious control instructions; Step S3: Use the energy controller to block the malicious control command and issue a warning; Step S4: The scheduling control commands are collected in real time by the command verification unit, and a security review is performed in conjunction with the current battery simulation parameters to determine the system's protection capability. If the malicious control command is detected, the protection test is deemed to have failed. If only the normal scheduling instruction is detected, the protection test is deemed to have passed, and the normal scheduling instruction is recorded and the test is reset.

6. The method for testing the network attack protection capability of a battery system according to claim 5, characterized in that, The battery simulation parameters include at least one of the following: cell voltage, cell current, cell temperature, battery state of charge, battery state of health, maximum voltage, minimum voltage, and maximum voltage difference.

7. The method for testing the network attack protection capability of a battery system according to claim 5, characterized in that, Step S2 further includes the following sub-steps: Based on the real-time status of the battery simulation unit, it is randomly positioned in either normal mode or attack test mode; in normal mode, the normal scheduling command is sent; in attack simulation mode, the malicious control command is sent.

8. An electronic device, characterized in that, The electronic device includes a processor and a memory, wherein the memory stores a computer program that can be executed by the processor, and when the processor reads the computer program in the memory, it performs the steps in the battery system network attack protection capability testing method as described in any one of claims 5-7.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps in the battery system network attack protection capability test method as described in any one of claims 5-7.

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