A Ball of Mass 3m, Moving at Speed V to the Right

Multiple Choice

A ball of mass 3m, moving at speed v to the right, approaches a ball of mass 2m, moving at speed 2v to the left. After the balls collide, what is the velocity of the center of mass?

A) v right
B) v/5 left
C) v/5 right
D) v left
E) Can't decide because we don't know whether this collision is inelastic or elastic