R. C. Barker makes purchasing decisions for his company. One product that he buys costs $50 per unit when the order quantity is less than 500. When the quantity ordered is 500 or more, the price per unit drops to $48. The ordering cost is $30 per order and the annual demand is 7,500 units. The holding cost is 10 percent of the purchase cost. How many units should R. C. order to minimize his total annual inventory cost?
A) 300
B) 306
C) 500
D) 200
E) None of the above