what is answer ??

XYZ firm is using a continuous review inventory system to order a certain spare part and is currently ordering 500 units of this part every time an order is placed. The part annual ordering cost is $800 and its annual holding cost is $400. To minimize the part's total annual inventory costs the firm should: Select one: O Reduce the order quantity so that it is less than 500 units O Add safety stock. Use a periodic inventory system to reduce costs. O Leave the order quantity at 500 units since it is the optimal order quantity O Increase the order quantity so that it is greater than 500 units Clear my choice