$\text { Find the derivative of the function } f ( x ) = 4 e ^ { x } \cos ( x ) \text {. Simplify your answer. }$

Multiple Choice

$\text { Find the derivative of the function } f ( x ) = 4 e ^ { x } \cos ( x ) \text {. Simplify your answer. }$

A) $4 e ^ { x } ( \cos ( x ) + \sin ( x ) )$
B) $- 4 e ^ { x } \sin ( x )$
C) $4 e ^ { x } \cos ( x )$
D) $4 e ^ { x } \sin ( x ) \cos ( x )$
E) $4 e ^ { x } ( \cos ( x ) - \sin ( x ) )$