Ball a has a mass of 5.0 kg. ball b has twice the mass of ball a. the two balls collide and stick together in a perfectly inelastic collision. after the collision the combined balls are at rest. if the velocity of ball a before the collision was 13 m/s, what was the velocity of ball b before the collision? a. 6.5 b. -6.5 m/s c. 26 m/s d. -13 m/s e. 0.0 m/s