For each of the following pairs of Treasury securities (each with $1,000 par value), identify which will have the higher price:
a. A three-year zero-coupon bond or a five-year zero-coupon bond?
b. A three-year zero-coupon bond or a three-year 4% coupon bond?
c. A two-year 5% coupon bond or a two-year 6% coupon bond?