Evaluate the Integral $\int 3 x e ^ { x } \mathrm {~d} x$

Multiple Choice

Evaluate the integral. $\int 3 x e ^ { x } \mathrm {~d} x$

A) $- 3 e ^ { x } ( x + 1 ) + C$
B) $3 e ^ { x } ( x + 1 ) + C$
C) $3 e ^ { x } ( x - 1 ) + C$
D) $3 e ^ { x } + C$
E) $- 3 e ^ { x } ( x - 1 ) + C$