Please show work.

An insurance company is analyzing the following three bonds, each with five years to maturity, annual interest payments, and is using duration as the measure of interest rate risk. What is the duration of each of the three bonds?

Duration of the bond years a. $10,000 par value, coupon rate = 8.2%, rb = 0.12 b. $10,000 par value, coupon rate = 10.2%, rb = 0.12 c. $10,000 par value, coupon rate = 12.2%, rb = 0.12