Find the Volume of the Described Solid $x$ -Axis At $x = - 3$

Multiple Choice

Find the volume of the described solid.
-The solid lies between planes perpendicular to the $x$ -axis at $x = - 3$ and $x = 3$ . The cross sections perpendicular to the $x$ -axis are semicircles whose diameters run from $y = - \sqrt { 9 - x ^ { 2 } }$ to $y = \sqrt { 9 - x ^ { 2 } }$ .

A) $9 \pi$
B) $36 \pi$
C) $72 \pi$
D) $18 \pi$