Determine All Critical Points for the Function $f ( x ) = x ^ { 3 } - 6 x ^ { 2 } + 9$

Multiple Choice

Determine all critical points for the function.
- $f ( x ) = x ^ { 3 } - 6 x ^ { 2 } + 9$

A) $x = 0$ and $x = 2$
B) $x = - 2$ and $x = 2$
C) $x = 0$
D) $x = 0$ and $x = 4$