Rocky Mountain Tire Center sells 10,000 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 $22 per tire if fewer than 200 tires are ordered, $18 per tire if 200 or more, but fewer than 8,000, tires are ordered, and $16 per tire if 8,000 or more tires are ordered.
A ) How many tires should Rock Mountain order each time it places an order?
Rocky Mountain's optimal order quantity is __ units (enter your response as a whole number)