Let $f ( x ) = x ^ { 3 } - 6 x ^ { 2 }$

Multiple Choice

Let $f ( x ) = x ^ { 3 } - 6 x ^ { 2 }$ Then which of the following is the largest interval, of those listed, for which $f ^ { \prime } ( x ) < 0$ for all x
In that interval?

A) $( 4 , \infty )$
B) $( - \infty , 0 )$
C) (0,4)
D) $( - \infty , 0 ) \cup ( 4 , \infty )$
E) $( - \infty , \infty )$