Solve the Problem $\frac { 121 } { 1984 }$ In

B)

Multiple Choice

Solve the problem.
-A reflecting telescope has a mirror shaped like a paraboloid of revolution. If the distance of the vertex to the focus is 31 feet and the distance across the top of the mirror is 66 inches, how deep is the mirror in the center? A) $\frac { 121 } { 1984 }$ in.

B) $\frac { 363 } { 496 }$ in.

C) $\frac { 961 } { 132 }$ in.

D) $\frac { 1089 } { 124 } \mathrm { in }$ .