PLEASE help my with the right answer please

Al Maha Company is specialized in mangoes distribution in the city of Muscat. Sales are 420 boxes per month (four weeks). It costs RO 100 to make and receive an order and holding cost is RO 4.5 per box per year. The prices per unit 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. What is the Economic Order Quantity while not consider the purchase cost? Round-up to the nearest integer Select one: O a. 170 O b. 574 O c. None is correct O d. 537 O e. 199