Could you please answer this question # 3 with explanation?

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QUESTION 10 A gift shop sells toy cars at a very steady pace of 10 per day, 310 days per year. The wholesale cost of the toy cars is $4.5, and the gift shop uses an annual interest rate of 20 percent to compute holding costs. The ordering cost is $30. If the supplier offers to sell the toys at $4.4 when the order size is greater than 600. How many toys should the store order to minimize the average cost