Alex is asked to move two boxes of books in contact with each other and resting on a rough floor. He decides to move them at the same time by pushing on box A with a horizontal pushing force Fo = 8.7 N. Here A has a mass my = 11.0 kg and B has a mass = 7.0 kg. The contact force between the two boxes is F. The coefficient of kinetic friction between the boxes and the floor is 0.04. (Assume Fp acts in the +x direction.) MA MB (a) What is the magnitude (in m/s2) of the acceleration of the two boxes? m/s2 (b) What is the force exerted on my by ma? In other words what is the magnitude (in N) of the contact force F? N (c) If Alex were to push from the other side on the 7.0-kg box, what would the new magnitude (in N) of F be