3. An insurance company is analyzing three bonds and is using duration as the measure of interest rate risk. All three bonds trade at a yield to maturity of 12 percent, have $10,000 par values, and have four years to maturity. The bonds differ only in the amount of annual coupon interest that they pay: 9, 12 and 15 percent. a) What is the duration for each four-year bond? b) What is the relationship between duration and the amount of coupon interest that is paid