A $$8,000$ bond had a coupon rate of $4\mathrm{.}50\%$ with interest paid semi$-$annually. John purchased this bond when there were $6$ years left to maturity and when the market interest rate was $4\mathrm{.}75\%$ compounded semi$-$annually. He held the bond for $2$ years, then sold it when the market interest rate was $4\mathrm{.}25\%$ compounded semi$-$annually.

a$.$ What was the purchase price of the bond?

Round to the nearest cent.

b$.$ What was the selling price of the bond?

Round to the nearest cent.

c$.$ What was John's gain or loss on this investment?

amount was $