6-29. The following table summarizes the yields to maturity on several one-year, zero-coupon securities: Security Yield (%) Treasury 3.1 AAA corporate BBB corporate B corporate 3.2 4.2 4.9 a. What is the price (expressed as a percentage of the face value) of a one-year, zero-coupon corporate bond with a AAA rating? b. What is the credit spread on AAA-rated corporate bonds? c. What is the credit spread on B-rated corporate bonds? How does the credit spread change with the bond rating? Why? d