Two crates, of mass m₁ = 74 kg and m2 = 135 kg,
are in contact and at rest on a horizontal surface. Force
F=630 N is exerted on the 74-kg crate. The
coefficient of kinetic friction is 0.18. (Figure 1)

Part A: determine the acceleration of the system

Part B: Determine the magnitude of the force that each crate exerts on the other

Part C: if the crates are reversed, determine the acceleration of the system

Part D: if the crates are reversed, determine the magnitude of the force that each crate exerts on the other