A ball (mass 0.40 kg) is initially moving to the left at 30 m/s. After hitting the wall, the ball is moving to the right at 20 m/s. What is the impulse of the net force on the ball during its collision with the wall?
A) 20 kg. m/s to the right
B) 20 kg. m/s to the left
C) 4.0 kg. m/s to the right
D) 4.0 kg. m/s to the left
E) none of the above