Solve the given problem:
Problem: A car of mass m moving at speed 25 m/s rear ends a truck of mass 2m moving in the same direction as the car, but a speed 16 m/s. the car is stuck to the truck, so they move off together with the same speed vf afterwards.
Part I: What is speed vf?
Part II: What amount of kinetic energy is lost in the collision if m=1400kg?
Please include each step and the equations and numbers you used. Thanks!