Four years after the issue of a $10,000, 9.5% coupon, 20-year bond, the rate of return required

Question:

Four years after the issue of a $10,000, 9.5% coupon, 20-year bond, the rate of return required in the bond market on long-term bonds was 7.8% compounded semiannually.
a. At what price did the bond then sell?
b. What capital gain or loss (expressed in dollars) would the original owner have realized by selling the bond at that price?