Find C So That the Following Can Serve as the Probability

Multiple Choice

Find c so that the following can serve as the probability density function of a random variable X: $$f ( X ) = \left\{ \begin{array} { l l } c \cdot X \cdot e ^ { - 4 \mathrm { x } ^ { 2 } } & \text { if } \mathrm { X } \geq 0 \\0 & \text { otherwise }\end{array} \right.$$

A) 8
B) 4
C) $\frac { 1 } { 8 }$
D) $\frac { 1 } { 4 }$
E) 1
F) 16

G) $\frac { 1 } { 16 }$
H) 2