Rocky Mountain Tire Center sells 8,000 ?go-cart tires per year. The ordering cost for each order is ?$35?, and the holding cost is 50?% of the purchase price of the tires per year. The purchase price is ?$24 per tire if fewer than 200 tires are? ordered, ?$19 per tire if 200 or? more, but fewer than 8,000?, tires are? ordered, and ?$13 per tire if 8,000 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).
b) What is the total cost of this policy?