Consider the following. a. What is the duration of a four-year Treasury bond with a 9 percent semiannual coupon selling at par? b. What is the duration of a three-year Treasury bond with a 9 percent semiannual coupon selling at par? c. What is the duration of a two-year Treasury bond with a 9 percent semiannual coupon selling at par? (For all requirements, do not round intermediate calculations. Round your answers to 2 decimal places. (e.g., 32.16))