Dynamic power management

Abstract

The invention relates to dynamic power management. A system and method of managing power consumption of an automated storage and retrieval system includes a container handling vehicle having a rechargeable power source that handles storage containers in the automated storage and retrieval system; a charging station for charging a rechargeable power source of the container carrying vehicle; a power supply that transmits power to the storage system; a power monitoring device coupled to the power supply; a control system controlling operation of the automatic storage and retrieval system; the power monitoring device monitors available power from a power source entering the automated storage and retrieval system and transmits a signal indicative of the available power to the control system, the control system responsive to the signal and in an event that the signal indicates that the available power has dropped below a threshold level, the power monitoring device transmits the signal to the control system. The power consumption of the respective container handling vehicles and / or charging stations is reduced by modifying the operational management power consumption of the container handling vehicles and / or charging stations, thereby providing modified operation of the automated storage and retrieval system during lower power availability.

Description

[0001] This application is a divisional application of the Chinese patent application with application number 202080025933.X. Technical Field

[0002] The present invention relates to a system and method for managing power consumption of an automated storage and retrieval system, and more particularly, to a system and method for managing power consumption of an automated storage and retrieval system by providing modified operation of the automated storage and retrieval system during periods when lower power is available. Background Art

[0003] Figure 1 A typical prior art automated storage and retrieval system 1 having a frame structure 100 is disclosed, and Figure 2 and Figure 3 Two different prior art container handling vehicles 201 , 301 suitable for operating on such a system 1 are disclosed.

[0004] The frame structure 100 includes a plurality of upright members 102 and a plurality of horizontal members 103 supported by the upright members 102. The members 102, 103 may be generally made of metal, such as extruded aluminum profiles.

[0005] The frame structure 100 defines a storage grid 104 that includes storage columns 105 arranged in rows in which storage columns 105 store containers 106 (also referred to as bins) that are stacked one upon another to form a stack 107. The storage grid 104 prevents horizontal movement of the stack 107 of storage containers 106 and guides vertical movement of the containers 106, but does not generally otherwise support the storage containers 106 when stacked.

[0006] Each prior art container handling vehicle 201, 301 includes a storage compartment or space for receiving and storing the storage container 106 while the storage container 106 is being transported on the rail system 108. The storage compartment may include a cavity centrally disposed within the vehicle body 201a, such as Figure 2 As shown in, and as described in, for example, WO 2015 / 193278 A1, the contents of which are incorporated herein by reference.

[0007] Figure 3 An alternative configuration of a container handling vehicle 301 having a cantilever configuration is shown. Such a vehicle is described in detail, for example, in NO 317366, the contents of which are also incorporated herein by reference.

[0008] In the storage grid 104, most of the grid columns 112 are storage columns 105, i.e., grid columns 105 in which storage containers 106 are stored in stacks 107. However, the grid 104 typically has at least one grid column 112 that is not used to store storage containers 106, but which includes a location where container handling vehicles 201, 301 can unload and / or pick up storage containers 106 so that they can be transported to an access station (not shown) where the storage containers 106 can be accessed from outside the grid 104 or transferred out of the grid 104 or into the grid 104. Such locations are typically referred to in the art as "ports," and the grid columns 112 in which the ports are located may be referred to as "port columns" 119, 120. Transport to the access station may be in any direction, i.e., horizontal, inclined, and / or vertical. For example, storage containers 106 may be placed in random or dedicated grid columns 112 within storage grid 104 and then picked up by any container handling vehicle and transported to ports 119, 120 for further transport to an access station. Note that the term "inclined" refers to the transport of storage containers 106 having a general transport orientation somewhere between horizontal and vertical.

[0009] When you want to access the storage Figure 1 104, one of the container handling vehicles 201, 301 is instructed to retrieve the target storage container 106 from its location in the grid 104 and transport it to the unloading port 119. This operation involves moving the container handling vehicle 201, 301 to a grid position above the storage column 105 where the target storage container 106 is located, retrieving the storage container 106 from the storage column 105 using a lifting device (not shown) of the container handling vehicle 201, 301, and transporting the storage container 106 to the unloading port 119. If the target storage container 106 is located deep within the pile 107, i.e., one or more other storage containers 106 are located above the target storage container 106, the operation also involves temporarily moving the storage containers located above before lifting the target storage container 106 from the storage column 105. This step is sometimes referred to in the art as "digging" and can be performed using the same container handling vehicle that is subsequently used to transport the target storage container to the unloading port 119, or using one or more other cooperating container handling vehicles. Alternatively or additionally, the automated storage and retrieval system 1 may have a container handling vehicle dedicated to the task of temporarily removing storage containers from the storage column 105. Once the target storage container 106 has been removed from the storage column 105, the temporarily removed storage container may be relocated to the original storage column 105. However, the removed storage container can alternatively be relocated to other storage columns.

[0010] When a storage container 106 is to be stored in the grid 104, one of the container handling vehicles 201, 301 is instructed to pick up the storage container 106 from the access port 120 and transport it to the grid position above the storage column 105 where it is to be stored. After removing any storage containers located at or above the target location within the storage column stack 107, the container handling vehicle 201, 301 positions the storage container 106 at the desired location. The removed storage container can then be lowered back into the storage column 105, or relocated to another storage column.

[0011] In order to monitor and control the automatic storage and retrieval system 1, for example, to monitor and control the positions of the individual storage containers 106 within the grid 104, the contents of each storage container 106, and the movement of the container handling vehicles 201, 301, so that the desired storage container 106 can be transported to the desired location at the desired time without causing the container handling vehicles 201, 301 to collide with each other, the automatic storage and retrieval system 1 includes a control system, which is typically computerized, and typically includes a database for tracking the storage containers 106.

[0012] NO 340313 B1 and WO 2012138235 A2 show the solutions envisaged by the preambles of the independent claims.

[0013] Storage systems like the ones described above consume energy by, for example, charging power sources in container handling vehicles. These power sources, typically lithium-ion batteries, can be charged at any given time of the day, as storage systems like these can be operated 24 hours a day, all year round. In the case of large storage systems with a large number of container handling vehicles, this can require a large amount of energy.

[0014] In a normal power grid, during certain periods of the day, power consumption is higher than normal. During these periods, there is a risk of overloading the power supply. One way to solve this problem could be to expand the power supply to accommodate the higher power consumption, however, this can be quite expensive and unnecessary, as only during certain periods of the day the power supply is insufficient.

[0015] Another solution could be to install local renewable power sources, such as solar cells. However, solar cells only work optimally when the daytime and weather conditions are right. Otherwise, the amount of electricity received from these types of sources is unreliable. Solar cells also have limited effectiveness in certain places around the globe and at certain times of the year. Other local renewable power sources, such as windmills and hydro turbines, also have limitations. Their working depends on location and weather conditions.

[0016] Therefore, it is desirable to solve the problem of overloaded power supply without having to expand it. Summary of the invention

[0017] The invention is set forth and characterized in the independent claim, while the dependent claims describe further characteristics of the invention.

[0018] The present invention is defined by a system for managing power consumption of an automated storage and retrieval system, comprising: a container handling vehicle having a rechargeable power source for handling storage containers in the automated storage and retrieval system; a charging station for charging the rechargeable power source of the container handling vehicle; a power supply for delivering power to the storage system; a power monitoring device coupled to the power supply; and a control system for controlling the operation of the automated storage and retrieval system, wherein the power monitoring device is arranged to monitor available power from a power source entering the automated storage and retrieval system and transmit a signal indicating the available power to the control system, wherein the control system is arranged to manage power consumption in response to the signal and in the event that the signal indicates that the available power has dropped below a threshold level by being configured to modify the operation of the container handling vehicle and / or the charging station to reduce the power consumption of the corresponding container handling vehicle and / or the charging station, thereby providing modified operation of the automated storage and retrieval system during periods of lower power availability.

[0019] Furthermore, the control system may be configured to adjust the speed of the at least one container handling vehicle based on available power, wherein the speed is reduced during periods when lower power is available.

[0020] The power supply system may be arranged to provide power from locally generated renewable energy sources and / or grid power.

[0021] The control system may control the number of charging stations operating normally by reducing the number of charging stations during periods of lower power availability, or the control system may adjust the charging power of the charging stations by reducing the charging power during periods of lower power availability. In addition, the control system may direct the container handling vehicle to the charging station with the highest charging capacity during periods of lower power availability.

[0022] The present invention is further described by a method for managing power consumption of an automatic storage and retrieval system, comprising: a container handling vehicle having a rechargeable power source for handling storage containers in the automatic storage and retrieval system; a charging station for charging the rechargeable power source of the container carrying vehicle; a power supply system for delivering power to the storage and retrieval system; a power monitoring device coupled to the power supply; a control system for controlling the operation of the automatic storage and retrieval system; wherein the method includes the following steps: monitoring the available power from the power source entering the automatic storage and retrieval system with the aid of the power monitoring device; transmitting a signal indicating the available power to the control system with the aid of the power monitoring device; allowing the control system to respond to the signal, and in the event that the signal indicates that the available power has dropped below a threshold level, managing power consumption by being configured to modify the operation of the container handling vehicle and / or the charging station to reduce the power consumption of the corresponding container handling vehicle and / or the charging station; and providing modified operation of the automatic storage and retrieval system during periods of lower power availability.

[0023] The invention is further defined by a computer program for adjusting and adapting the power consumption of the storage system when executed in a processor in a control system, and an automatic storage and retrieval system having its power consumption managed by a system for managing power consumption.

[0024] Therefore, by adapting the charging strategy of the system, power consumption can be reduced. The adaptation of the charging strategy can be to reduce the need to charge the battery during these time periods. To reduce the need for charging, the container carrier vehicle can be operated at a reduced speed, thereby reducing the need to charge the battery on the vehicle.

[0025] In addition, the charging level of the charging station can be reduced to reduce the power consumption of the system during periods of insufficient power supply. In addition, the system can guide vehicles with batteries that need charging during these time periods to the charging station with the highest capacity.

[0026] Therefore, the solution is to install power monitoring equipment in the power supply to keep track of the available power at all times. This information is transmitted to the system, which can adjust its power consumption accordingly. The system can also track periods of low power supply to see if there are certain recurring periods of time during the day when the available power is low. The system can use this information to adjust power consumption to accommodate upcoming periods of low power supply. This could be to reduce the speed of the vehicle before a period of low power supply to extend the range of the battery on the vehicle, and to charge the battery on the vehicle before it is properly charged. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a perspective view of a grid of a prior art automated storage and retrieval system.

[0028] Figure 2 is a perspective view of a prior art container handling vehicle having a centrally disposed cavity for receiving a storage container therein.

[0029] Figure 3 is a perspective view of a prior art container handling vehicle having a cantilever for receiving a storage container underneath.

[0030] Figure 4 It is a block diagram of how the different parts of the system are connected.

[0031] Figure 5 is a flow chart of a process for monitoring and adjusting power consumption in accordance with the present invention.

[0032] Figure 6 is a diagram showing an example of the present invention in use. DETAILED DESCRIPTION

[0033] Figure 1 is a perspective view of a grid of a prior art automated storage and retrieval system.A typical prior art automated storage and retrieval system 1 having a frame structure 100 is disclosed.

[0034] The frame structure 100 includes a plurality of upright members 102 and a plurality of horizontal members 103 supported by the upright members 102. The members 102, 103 may be generally made of metal, such as extruded aluminum profiles.

[0035] The frame structure 100 defines a storage grid 104 comprising storage columns 105 arranged in rows, wherein storage columns 105 storage containers 106 (also referred to as boxes) are stacked one upon another to form stacks 107 .

[0036] Figure 2 is a perspective view of a prior art container handling vehicle having a centrally disposed cavity for receiving a storage container therein. Figure 2 and Figure 3 Two different prior art container handling vehicles 201 , 301 suitable for operating on such a system 1 are disclosed.

[0037] Each prior art container handling vehicle 201, 301 includes a storage compartment or space for receiving and storing the storage container 106 while the storage container 106 is being transported on the rail system 108. The storage compartment may include a cavity centrally disposed within the vehicle body 201a.

[0038] Figure 3 is a perspective view of a prior art container handling vehicle having a cantilever for receiving storage containers underneath. An alternative configuration of a container handling vehicle 301 having a cantilever configuration is shown.

[0039] Figure 4 is a block diagram of how the different parts of the system are connected. Power supply 401 provides power to the storage system for operation. The power can come from the normal grid or from a locally deployed renewable power source, or both. The locally deployed power source is most likely a solar cell, but can also be a wind turbine or a hydro turbine.

[0040] A power monitoring device 402 is mounted to the power supply 401. The power monitoring device 402 continuously monitors the amount of power available from the grid. The reading of the amount of power available is sent to the control system 403. The control system 403 tracks whether there are specific time periods during the day when the power supply 401 is insufficient to power the entire system. If such time periods are expected, the control system 403 will adjust the power consumption of the system so as not to overload the power supply 401.

[0041] If the control system 403 receives information from the power monitoring device 402 that the power supply 401 is insufficient, the control system 403 may modify the power consumption. The control system 403 may modify the power consumption by reducing the charging effect of the charging station 404. If the charging station 404 charges the battery with a reduced effect, the power consumption is reduced.

[0042] An alternative solution is to modify the speed of the container handling vehicle 201, 301. The reduction in speed ensures that the rechargeable batteries on board the container handling vehicle 201, 301 last longer before having to be recharged. Alternatively, both strategies may be used simultaneously.

[0043] The power consumption can also be modified to accommodate fluctuations in electricity prices during the day, for example if there are periods during the day when prices are high.

[0044] The algorithm determines whether to use one or both solutions to reduce the power consumption of the storage system, and the decision is based on historical data when power supply is insufficient and information about available power from power monitoring equipment.

[0045] These two different ways of reducing power consumption can be used to quickly reduce power consumption to accommodate a sudden unexpected drop in power availability, or they can be used to reduce power consumption based on a historical mapping of recurring time periods of drop in power availability.

[0046] Depending on the drop in available power, these two different techniques for reducing power consumption can be used together or separately. The algorithm determines which solution to use based on different factors, such as whether the drop in available power was expected, how severe it is, and how long the surge has lasted or is expected to last.

[0047] One solution is to reduce the charging effect but maintain the operating speed of container handling vehicles.

[0048] This solution results in a sudden drop in power consumption and is ideal for handling unexpected drops in power availability. Alternatively, the method can be used to handle short-term and expected drops in power availability.

[0049] Alternatively, if there is excess power available, such as due to a windy or particularly sunny day, the excess power can be used to supplement the rechargeable power source.

[0050] As an alternative solution, a reduction in the charging effort and a reduction in the speed of the container handling vehicle 201, 301 may be implemented. This solution is effective if there is an expected drop in available power that is expected to last for a longer period of time, such as several hours.

[0051] A third alternative is to keep the charging station at 100% charge but reduce the speed of the container handling vehicle. This alternative is effective if there is an expected drop in available power, where it is desirable to prepare as many fully charged batteries as possible when the available power drops.

[0052] It is also possible to first reduce the power consumption of the charging station 404 and then reduce the speed of the container handling vehicle 201 , 301 if the surge in power consumption is longer than expected.

[0053] As an additional possibility, the container handling vehicles 201, 301 can reduce their speed and the charging stations 404 can reduce their charging effect after a period of time. This solution is preferred if there is an expected power drop that is expected to last for a long time. In this solution, the container handling vehicles 201, 301 conserve their energy and the charging effect is maximized until a drop in power availability occurs.

[0054] In a preferred embodiment of the invention, the charging system comprises a plurality of chargers connected in a charging group. There may be several such charging groups in the whole system. A charging group is defined by a group of chargers connected to the same power supply circuit.

[0055] The control system 403 can optimize and distribute the load between the charging groups. In addition, the control system can optimize and distribute the load within the charging group by adjusting the charging curve of each charger. This is to optimize the use of the available power for each charging group. Based on the known operations and tasks given by the empirical data obtained from the empirical model and the future tasks, the available power is optimized.

[0056] Optimizing and distributing the load between charge groups is accomplished by monitoring the available power for each charge group. This is accomplished by communicating the available effects of the circuits powering the individual charge groups. Alternatively, the available power may be statistically set for each charge group without periodically updating the actual available power.

[0057] In addition, the energy demand of each charger included in each charging group is monitored. The energy demand will depend on whether the charger is active and where the charger is in the charging process. By evaluating the data from each charger, the future required effect of the associated charger can be estimated.

[0058] Evaluate the current and future energy needs of the system. This is done based on the current energy level, the system's activity and future tasks, the current and future needs in the charging group, and the energy needs of the system based on an empirical model. Update the model using empirical data.

[0059] The load sharing between charging groups is optimized by using the current and estimated future energy requirements of each individual charging group to distribute new charging tasks between the groups.

[0060] The use within the charging group is optimized by adjusting the charging profile of each individual charger. The available power of the charging group is continuously monitored and the available power is always distributed between the individual chargers. Here, when adjusting the internal consumption in the charging group, the estimated future effect required by each individual charger is also taken into account.

[0061] The control system will continuously update empirical models and algorithms based on historical data.

[0062] Figure 5 is a flow chart of a process for monitoring and adjusting power consumption in accordance with the present invention.

[0063] The power monitoring device 402 monitors the available power from the power supply 401. The power supply 401 can be a grid solution or a local renewable power source, such as solar cells or similar. Most likely, the power supply 401 is power from the grid, or a combination of grid power and power from a local renewable power source.

[0064] The power monitoring device 402 transmits the available power to the control system 403. This data is stored in an empirical model and provides a basis for how the control system handles future drops in available power. The control system 403 can implement measures for handling sudden drops in available power and predicting future power shortages.

[0065] The control system evaluates whether the available power is sufficient to power the entire storage system. If it is sufficient, operation continues at the current level. If it is not sufficient, the control system can initiate actions to reduce the power consumption of the system.

[0066] These actions can modify the charging effect of the charging station. In addition, the control system can modify the operating speed of the container handling vehicle.

[0067] A speed modification might be to reduce the speed of a container handling vehicle by 50%, thereby allowing a fully charged container handling vehicle to run twice as long without having to recharge the battery.

[0068] In addition, the control system tracks time periods when there is a drop in available power. This data is stored in an empirical model so the control system can predict when available power will drop so it can adjust power consumption in advance.

[0069] In a preferred embodiment of the invention, the charging system consists of a plurality of chargers connected in a charging group. There may be several such charging groups in the whole system. A charging group is defined by a group of chargers connected to the same power supply circuit.

[0070] The charging effect within a charging group can be optimized by operating some chargers at full capacity and allowing other chargers to operate at reduced capacity or shut down completely. The internal division of capacity is determined by the tasks the chargers are performing and the tasks the chargers are intended to perform.

[0071] The distribution of the load between the different charging groups is accomplished by monitoring the available power to each charging group and the available efficiency of the circuits delivering power to the various charging groups.

[0072] Figure 6 is a diagram showing an example of the invention in use. In this example, there is a storage system using three container handling vehicles. Each container handling vehicle has an effect of 100W. This results in a combined effect of 300W for all three container handling vehicles. Due to peak operating times during certain hours of the day, the system requires three chargers to keep all container handling vehicles running at all times. A typical charger has an effect of 1200W. Therefore, the system needs to be sized to handle 3600W.

[0073] Without power management, the system is sized for 3600W, even though 3600W is actually needed only during certain periods of the day. Sizing the system in this way results in a significant investment in the power supply, in addition to the storage system itself. If we now scale up the system to 400 container handling vehicles and 200 chargers, the power supply needs to be sized for 240kW, and it is easy to see how expensive this is.

[0074] However, if we use an empirical model, where empirical data is used to update the model in order to predict when surges in electricity demand will occur, we can adjust the charger’s charging strategy to accommodate these surges.

[0075] If we can use empirical models to predict surges, we can adjust the charger’s charging strategy to start charging the battery before the surge arrives and continue charging after the surge has passed. Thus, we are able to spread the use of power over a longer period of time and, therefore, reduce the size of the system’s power supply.

[0076] In the example of three container handling vehicles, we were able to reduce the charging effect to 1000W by using empirical models and still maintain full operation the entire time. Therefore, the cost of installing such a storage system is greatly reduced.

[0077] exist Figure 6 In the example shown, line A describes the power demand in a storage system without an empirical model. Here we can see that the surge in power demand starts at 8 o'clock and continues until 12 o'clock, with a peak at 9 o'clock to 10 o'clock. Line B represents the maximum amount of power that the system can deliver, which is 3600W.

[0078] Line C shows the power demand in the same system, with the empirical model controlling the charger’s charging strategy. Here we see that power usage is dispersed throughout the day, with a peak of just 1000W. Line D shows the maximum amount of power the system needs to deliver during the day, with the empirical model controlling the charger’s charging strategy.

[0079] Using this type of charging strategy, the user of the system may be forced to accept that during certain times of the day, the system will not be fully operational due to reduced costs of installing and sizing the system. The reduction in speed of container handling vehicles during certain times of the day may be a result of using an empirical model.

[0080] Machine learning and artificial intelligence can be used to maintain the empirical model and control the charging strategy of the charger.

Claims

1. A control system (403) for managing power consumption of an automated storage and retrieval system (1), the automated storage and retrieval system (1) comprising: - said control system (403), - a container handling vehicle (201, 301) having a rechargeable power source for handling storage containers in the automated storage and retrieval system (1), - a charging station (404) for charging the rechargeable power source of the container handling vehicle (201, 301), - a power supply (401) for delivering power to the automated storage and retrieval system (1), a power monitoring device (402) coupled to the power supply (401) and arranged to monitor fluctuations in the price of power from the power supply entering the automated storage and retrieval system and to transmit a signal indicative of the price of power to the control system (403), Wherein the control system (403) is arranged to respond to the signal and manage power consumption by being configured to: reducing the speed of the container handling vehicle (201, 301), and / or reducing the charging power of the charging station (404), to reduce power consumption of the container handling vehicle and / or the charging station in the event that the signal indicates that the price of electricity has increased above a threshold level, Thereby providing for modified operation of the automated storage and retrieval system during periods of high electricity prices.

2. The control system according to claim 1, wherein: The control system (403) is arranged to control the number of the charging stations (404) operating normally by reducing the number of the charging stations during periods of high electricity prices.

3. A control system according to any preceding claim, wherein: The control system (403) is configured to direct the container handling vehicle (201, 301) to the charging station (404) having the highest charging capacity during periods of high electricity prices.

4. The control system according to claim 1 or 2, wherein: The power supply (401) is arranged for providing power from locally generated renewable energy sources and / or grid power.

5. The control system according to claim 1 or 2, wherein: The control system (403) is configured to direct the container handling vehicle (201, 301) to the charging station (404) with the highest charging capacity during periods of high electricity prices, and the power supply (401) is arranged to provide power from locally generated renewable energy and / or grid power.

6. A method for managing power consumption of an automated storage and retrieval system (1), the automated storage and retrieval system comprising: a container handling vehicle (201, 301) having a rechargeable power source for handling storage containers in the automated storage and retrieval system (1); a charging station (404) for charging the rechargeable power source of the container handling vehicle (201, 301); a power supply (401) for delivering power to the automatic storage and retrieval system (1); a power monitoring device (402) coupled to the power supply system (401); a control system (403) for controlling the operation of the automatic storage and retrieval system, Wherein, the method comprises the following steps: - monitoring, by means of a power monitoring device (402), fluctuations in the price of electricity from said power supply entering said automated storage and retrieval system, - transmitting, by means of the power monitoring device (402), a signal indicative of the price of the power to the control system, - allowing the control system (403) to react to the signal and manage power consumption by being configured to: reducing the speed of the container handling vehicle (201, 301), and / or reducing the charging power of the charging station (404), to reduce power consumption of the container handling vehicle and / or the charging station in the event that the signal indicates that the price of electricity has increased above a threshold level, and - to provide modified operation of the automated storage and retrieval system during periods of high electricity prices.

7. The method according to claim 6, wherein: Power consumption is managed by allowing the control system (403) to adjust the number of charging stations (404) operating normally.

8. The method according to claim 6 or 7, wherein: Power consumption is managed by allowing the control system (403) to direct the container handling vehicle (201, 301) to the charging station (404) with the highest charging capacity.

9. The method according to claim 6 or 7, wherein: Power consumption is managed by allowing the power supply (401) to receive power from locally generated renewable energy sources and / or grid power.

10. The method according to claim 6 or 7, wherein: Power consumption is managed by allowing the control system (403) to direct the container handling vehicle (201, 301) to the charging station (404) with the highest charging capacity, and by allowing the power supply (401) to receive power from locally generated renewable energy and / or grid power.

11. A computer readable recording medium storing a computer program which, when executed in a processor in a control system (403), adjusts and adapts the power consumption of an automatic storage and retrieval system (1) according to the method of any one of claims 6 to 9.

12. An automated storage and retrieval system, the power consumption of which is managed by a control system (403) according to any one of claims 1 to 5.

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