Let $f ( x ) = \mathrm { e } ^ { \cos ( 3 x ) }$

Multiple Choice

Let $f ( x ) = \mathrm { e } ^ { \cos ( 3 x ) }$ Then $f ^ { \prime } ( x )$ is

A) $3 e ^ { \sin ( 3 x ) }$
B) $e ^ { 3 x } \sin ( 3 x )$
C) $3 e ^ { 3 x } \sin ( 3 x )$
D) $3 \sin ( 3 x ) \mathrm { e } ^ { \cos ( 3 x ) }$
E) $- 3 \sin ( 3 x ) \mathrm { e } ^ { \cos ( 3 x ) }$