PLEASE help my with the right answer please

Al Maha Company is specialized in mangoes distribution in the city of Muscat. Sales are 400 units per month. It costs OR 10 to make and receive an order and holding cost is OR 3.5 per unit per year. The prices depend on quantities purchased such that the order quantities from 1 to 199 at a unit price RO 5; quantity 200 to 499 at a unit price 4.5 RO; and quantity 500 and more at a per unit price of 4 RO. If the discount option is considered, then the best order quantity that minimizes the total annual inventory cost is Select one: O a. None is correct O b. 199 O c. 200 O d. 176 e. 500