6. Rank the durations or effective durations of the following pairs of bonds:

a. Bond A is an 8% coupon bond, with a 20-year time to maturity selling at par value. Bond B is an 8% coupon bond, with a 20-year maturity time selling below par value.

b. Bond A is a 20-year noncallable coupon bond with a coupon rate of 8%, selling at par. Bond B is a 20-year callable bond with a coupon rate of 9%, also selling at par.