Rocky Mountain Tire Center sells 6,000 ?go-cart tires per year. The ordering cost for each order is ?$40, and the holding cost is 50% of the purchase price of the tires per year. The purchase price is ?$19 per tire if fewer than 200 tires are? ordered, ?$17 per tire if 200 or? more, but fewer than 5000?, tires are? ordered, and ?$15 per tire if 5000 or more tires are ordered. ?a) How many tires should Rocky Mountain order each time it places an? order? Rocky? Mountain's optimal order quantity is ? units ?(enter your response as a whole? number).