A ball of mass m1 = 0.205 kg and velocity 1.59î m/s collides elastically with a ball of mass m2 = 0.306 kg and velocity −0.399î m/s. Assume the collision is head-on. (Express your answers in vector form. Due to the nature of this problem, do not use rounded intermediate values in your calculations)

(a)
Find their velocities after the collision (in m/s).
v1f=?
v2f=?

(b)
Find the velocity of their center of mass before and after the collision (in m/s).
vcm before=?
vcm after=?