Carts A and B are on a level, frictionless, one-dimensional ... ...

  Carts A and B are on a level, frictionless, one-dimensional track. Cart A (1 kg) is initially going right at 7 m/s, and Cart B (3 kg) is initially going left at 3 m/s. Cart A rebounds with a speed 3 m/s. What is the velocity of Cart B after the collision?
(A) 2.67 m/s, to the left
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in 08. Momentum