Solve the Problem $28 \mathrm { ft }$ And the Vertical Clearance Must Be

Solve the problem.
-A railroad tunnel is shaped like a semiellipse. The height of the tunnel at the center is $28 \mathrm { ft }$ and the vertical clearance must be $26 \mathrm { ft }$ at a point $18 \mathrm { ft }$ from the center. Find an equation for the ellipse.

A) $\frac { x ^ { 2 } } { 2352 } + \frac { y ^ { 2 } } { 676 } = 1$
B) $\frac { x ^ { 2 } } { 784 } + \frac { y ^ { 2 } } { 2352 } = 1$
C) $\frac { x ^ { 2 } } { 324 } + \frac { y ^ { 2 } } { 784 } = 1$
D) $\frac { x ^ { 2 } } { 2352 } + \frac { y ^ { 2 } } { 784 } = 1$