An observer sights on a bench mark with an elevation of $5\mathrm{.}25$ ft $,$ and reads a backsight of $2\mathrm{.}52$ ft $.$ The foresight rod reading that is necessary to find a point on the ground with an elevation of $2\mathrm{.}00$ ft is most nearly

$($A$)2\mathrm{.}73$ ft

$($B$)5\mathrm{.}25$ ft

$($C$)5\mathrm{.}77$ ft

$($D$)7\mathrm{.}77$ ft