pls help explain the formula and the calculation. thank you in advance .

cent redeemed at par ($1,000). Il lit what is the yield to maturity? 7-9. (Bond valuation) National Steel's 15-year, $1,000 par value bonds pay 5.5 per ent interest annually. The market price of the bonds is $1,085, and your required rate of return is 7 percent. a. Compute the bond's expected rate of return. b. Determine the value of the bond to you given your required rate of return. c. Should you purchase the bond? e $70 in annual interest, with a