7. A household electric appliance company plans to order electric fans for stocking up for the summer. The company decided to order the electric fans from a supplier, and it will incur an ordering cost at $500 per order. The annual demand of the electric fans is 49,000 Inventory-carrying cost is 40 percent per year. The purchasing price scheme is as follows: orders of less than 650 electric fans will cost the company $300 per unit; between 650 and 750 electric fans will cost $260 per unit; and 750 units or more will cost $230 per unit. Prices apply inclusively to all units bought. What is the optimum purchase order size that should be placed, and what is the total cost