Solve the Problem $A ( x ) = x \sqrt { 768 - x }$

Multiple Choice

Solve the problem.
-A rectangle that is x feet wide is inscribed in a circle of radius 16 feet. Express the area of the rectangle as a function of x.

A) $A ( x ) = x \sqrt { 768 - x }$
B) $A ( x ) = x ^ { 2 } \sqrt { 512 - x ^ { 2 } }$
C) $\mathrm { A } ( \mathrm { x } ) = \sqrt { 1024 - \mathrm { x } ^ { 2 } }$
D) $\mathrm { A } ( \mathrm { x } ) = \mathrm { x } \left( 1024 - \mathrm { x } ^ { 2 } \right)$