21. A 30 -year maturity, 7% coupon bond paying coupons semiannually is callable in five years at a call price of $1,100. The bond currently sells at a yield to maturity of 6% (3\% per half-year). a. What is the yield to call? b. What is the yield to call if the call price is only $1,050 ? c. What is the yield to call if the call price is $1,100 but the bond can be called in two years instead of five years