help please

(Assume par value for all bonds to be $1,000 unless specified otherwise) a. What is the YTM on a 15-year zero-coupon bond that currently sell for 65 percent of par value? b. Megathon Inc has bonds which have 8 years remaining to maturity, a YTM of 5.1 percent, and a current price of $964. The bonds make semiannual payments. What must the coupon rate be on these bonds? c. What is the price of a 25 -year, 6% coupon bond, assuming semiannual interest payments, if the YTM is 6.3\%