Need to calculate cost minizing order size, need solution asap

Q.2. (10 Marks) The annul demand for an item of inventory is 90 units. The item costs 300 a unit to purchase, the holding cost for one unit for one year is 18% of the unit cost and ordering costs are 400 an order. The Supplier offers a 5% discount for orders of 150 units or more, and a discount of 12% for orders of 180 units or more. 1 Required: Calculate the cost-minimizing order size