Four years ago you purchased a $10-$year $3\%$ coupon bond. At that time, the market rate of interest was $3\mathrm{.}60\%.$ Today, you sell the bond $($the current market rate of interest is $5\mathrm{.}40\%).$ For all parts, do not enter the $ or $\%$ sign, keep prices as positive, and keep $2$ decimal places. E$.$g$.$ enter $-$$$3\mathrm{.}456$ as $3\mathrm{.}46$ and $-9\mathrm{.}876\%$ as $-9\mathrm{.}88.$

$($c$)$ What rate of return did you earn on your investment over the $4-$year period that you held the bond?