You are trying to compare the interest rate risks of two bonds: (i) a 15-year 8% bond, and (ii) a 10-year 6% bond. Both bonds pay semi-annual interest payments. The current market interest rate for the 15-year bond is 7.2% and the market interest rate for the 10-year bond is 5.8%. a. Determine the (Macaulay) durations of the two bonds. b. Based on your findings in (a) and (b), which bond has a greater interest rate risk? Explain