Figure 12.69 is a contour diagram of the monthly payment on a 5 -year car loan as a function of the interest rate and the amount you borrow. The interest rate is $13 \%$ and you borrow $\$ 6000$ for a used car.
(a) What is your monthly payment?
(b) If interest rates drop to $11 \%$, how much more can you borrow without increasing your monthly payment?
(c) Make a table of how much you can borrow without increasing your monthly payment, as a function of the interest rate.
(FIGURE CANNOT COPY)