If  it costs $1 to store a box for a year, the order size is 400 units and the number times a year should the orders be placed to minimize inventory costs is 10 times.
Economic order quantity:
Using this formula to determine the economic order quantity
EOQ = √[2 (setup costs)(demand rate)] / holding costs.
Let plug in the formula
EOQ =√(2× 20× 4000)/1
EOQ = √160,000
EOQ = 400 units
Number of orders: Â Â
Number  of orders = Annual Demand / EOQ
Number of order = 4000/400
Number of order  = 10 times
Therefore the EOQ is 400 units and the number of orders is 10.
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