Rocky Mountain Tire Company sells $20,000$ go$-$cart tires per year. The ordering cost for each order is $$40,$ and the holding cost is $20\%$ of the purchase price of $$20$ per tire. They use a single supplier for their tires. Given the above information, please answer the following questions:

a$)$ How many tires should Rocky Mountain order each time they place an order?

b$)$ What would the total cost of this order quantity be$?$