HOW DO YOU GET 2000 as the ANSWER

the answer is 2000. thats all the info i have. i just need the explanation how to get the answer (2000).

Your company imports decorative planters from Italy. Weekly demand is 1,500 units on average, with a standard deviation of 800 . Each planter costs you $10, and the holding cost per year is 25%. You are using a distribution center in Arizona, and fixed transportation costs from Italy is $10,000 per order. Consider a 52-week/year operation. Consider a periodic review policy with a base stock level of 9,000 units. If the current inventory position is 7,000 units when you are about to order (similar to the idea of reorder point under continuous review), what should be your order quantity? a) 2000