The following table summarizes the yields to maturity on several one-year, zero-coupon securities: Security Treasury AAA corporate BBB corporate B corporate Yield (%) 3.14 3.23 4.23 4.89 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? d. How does the credit spread change with the bond rating? Why