Find the X-Values of All Relative Maxima of the Given $y = \frac { 1 } { 3 } x ^ { 3 } - 4 x ^ { 2 } + 12 x + 9$

Multiple Choice

Find the x-values of all relative maxima of the given function. $y = \frac { 1 } { 3 } x ^ { 3 } - 4 x ^ { 2 } + 12 x + 9$

A) $x = 0$
B) $x = 6$
C) $x = 4$
D) $x = 2$
E) no relative maxima