A 8-year annual coupon bond is currently selling for its par value of $ 1,000 with an annual yield of 6%. If the bond is callable at par, what is the effective duration of the bond, assuming rates change by 0.5%?

A 25 - year zero coupon bond with a face value of $1,000 is currently selling for $215.67. Using the bond's modified duration, what is the approximate change in the price of the bond if interest rates decline by 20 basis points?