A mass A of 0.8 kg moving to the right with a speed of 5 m/s collides head-on with a mass B of 1.2 kg moving in the opposite direction with a speed of 4 m/s. After the collision, A is moving to the left with a speed of 4 m/s. Find the velocity of B after collision and the coefficient of restitution.

A mass A of 0.8 kg moving to the right with a speed of 5 m/s collides head-on with a mass B of 1.2 kg moving in the opposite direction with a speed of 4 m/s. After the collision, A is moving to the left with a speed of 4 m/s. Find the velocity of B after collision and the coefficient of restitution.