9 (Newton's Third Law) Two boxes are in an elevator, stacked as shown. The elevator is moving upward (in the -direction), and it has a -acceleration of = 4 m/s2. Box A has a mass of 4 kg and box B has a mass of 10 kg. A. Is the elevator speeding up or slowing down? a. Speeding up b. Slowing down B. What is the -component of the normal force of block B on block A, , in Newtons? Hint: Draw a free-body diagram for block A. C. What is the -component of the normal force of block A on block B, , in Newtons? Hint: Use Newton's third law. D. What is the -component of the normal force of elevator floor on block B, , in Newtons? Hint: Draw a free-body diagram either for just B, or for the combined AB system - either works