15. The annual demand for an item of inventory is 2400 units. The order processing costs amount to Rs 350 per order. Inventory holding costs are estimated to be 2 per cent per month of the value of inventory. The normal price of the product is Rs 10 per unit. However, the supplier offers a quantity discount of 7 .5 per cent on an order of at least 400 units, and 12.5 per cent on an order of 600 units or more. Determine the EOQ.