4) Two objects, A with mass of 3.0 kg and object B with mass of 1.0 kg, move on a frictionless horizontal surface. Object A moves to the right at a constant velocity of 5.0 m/s, while object B moves to the left at a constant velocity of -2.0 m/s. They collide and bounce off one another (a perfectly elastic collision). Object A is now moving to the left at -2.0 m/s, A. Determine the total momentum of the system (both objects) before the collision B. What is the velocity of object B after the collision?