Truck and Car Collide

A heavy truck with mass $M = 5000$ kg is travelling at 20 m/sec to the right. It collides head on with a passenger car with mass $m = 2000$ kg travelling at 20 m/sec to the left. The two vehicles stick together and are carried down the road with locked brakes. The coefficient of kinetic friction between their tires and the road is $\mu_k = 0.3$. Find:

a) The velocity of the wrecked vehicles immediately after the collision (before friction has had any effect).

b) The energy dissipated during the collision.

c) How far the locked vehicles skid down the road after the collision before coming to rest.