Please answer correctly, I will give a thumbs up if A and B are correct ! thank you

Rocky Mountain Tire Center sells 12,000 go-cart tires per year. The ordering cost for each order is $40, and the holding cost is 30% of the purchase price of the tires per year. The purchase price is $19 per tire if fewer than 200 tires are ordered. $16 per tire if 200 or more, but fewer than 5,000, tires are ordered, and $13 per tire if 5.000 or more tires are ordered a. How many tires should Rocky Mountains tire order each time it time it places an order? b. What is the total cost of this policy? please show work