Choose the One Alternative That Best Completes the Statement or Answers

Choose the one alternative that best completes the statement or answers the question.
-A farmer's silo is the shape of a cylinder with a hemisphere as the roof. If the height of the silo is 66 feet and the radius of the hemisphere is $r$ feet, express the volume of the silo as a function of $r$ .

A) $V ( r ) = \pi ( 66 - r ) r ^ { 2 } + \frac { 2 } { 3 } \pi r ^ { 3 }$
B) $V ( r ) = \pi ( 66 - r ) + \frac { 4 } { 3 } \pi r ^ { 2 }$
C) $V ( r ) = \pi ( 66 - r ) r ^ { 3 } + \frac { 4 } { 3 } \pi r ^ { 2 }$
D) $V ( r ) = 66 \pi r ^ { 2 } + \frac { 8 } { 3 } \pi r ^ { 3 }$