I can't figure this out

A train car with mass m, = 637 kg is moving to the right with a speed v = 7.6 m/s and collides with a second stationary train car with mass my = 703 kg. The two cars latch together during the collision. Figure 1 (a) What is the final speed of the train cars latched together? (2pt) (b) What is the change in the kinetic energy of the two car system during the collision? (3pt) (c) What is the change in the momentum of the first car during the collision? (4pt) IFLINI 10 20 30 40 50 t (ms) Figure 2: (d) The force during the collision is shown in Fig. 2. What is the magnitude of the maximum force, Fmar, exerted on the first car during the collision? (3pt) m Figure 3: (e) Now the same two cars are involved in a second collision. The first car is again moving to the right with a speed vi = 7.6 m/s and collides elastically with the second train car that is now moving to the left with a speed u2 - 8.4 m/s before the collision. What are the velocities of the cars after the collision? (A positive velocity means the train car moves to the right, a negative velocity means the train car moves to the left.) (4pt) (f) After the collision, the second car moves to the right and encounters a rough surface. It eventually comes to a stop after travelling distance d = 10.0 m. What is the coefficient of kinetic friction of the rough surface? (4pt)