A car dealer offers a purchase option and a lease option on all new cars. Suppose you are interested in a car that can be bought outright for $25,000 or leased for a start-up fee of $1200 plus monthly payments of $350.

a. Find the linear function y = f(m) that gives the total amount you have paid on the lease option after m months.

b. With the lease option, after a 48-month (4-year) term, the car has a residual value of $10,000, which is the amount that you could pay to purchase the car. Assuming no other costs, should you lease or buy?