A $$2,500$ bond had a coupon rate of $6\mathrm{.}50\%$ with interest paid semi$-$annually. Cody purchased this bond when there were $7$ years left to maturity and when the market interest rate was $7\mathrm{.}50\%$ compounded semi$-$annually. He held the bond for $2$ years, then sold it when the market interest rate was $3\mathrm{.}50\%$ compounded semi$-$annually.

Calculate his gain or loss on this investment.

a$.$

$-$$$133\mathrm{.}12$

b$.$

$$475\mathrm{.}55$

c$.$

$$38\mathrm{.}78$

d$.$

$$608\mathrm{.}66$