Differentiate the Given Function $$f ( x ) = e ^ { - 3 x }$$

Multiple Choice

Differentiate the given function. $$f ( x ) = e ^ { - 3 x }$$

A) $- 3 e ^ { - 3 x }$
B) $- 3 x e ^ { - 3 x }$
C) $e ^ { - 3 x }$
D) $e ^ { - 3 x / 3 }$