Assume that all interest rates in the economy decline from 10 percent to 9 percent. Which of the following bonds will have the smallest percentage increase in price? Select one:

a. A 13-year zero coupon bond.

b. An 18-year bond with a 9% coupon.

c. A 10-year bond with a 10% coupon.

d. A 15-year zero coupon bond.

e. A 10-year bond with a 20% coupon.