Given:

A crest and sag curve connect a $\backslash (-2\mathrm{.}5\backslash \%\backslash )$ road segment with a positive grade road segment $($see figure below$).$ The crest and sag curves required to connect the ramp should be connected with a constant$-$grade section with $\backslash (-5\mathrm{.}0\backslash \%\backslash )$ grade. The design speed is assumed as $55$ MPH and the elevation difference is $28$ ft $.$ The PVC on the crest curve is at station $\backslash (26+89\backslash )$ and the PVT on the sag curve is $\backslash (41+51\backslash ).$

Find:

The final grade of the sag curve.