A car with mass m = [06] kg is initially traveling directly east with a speed vi = 25.0 m/s. It crashes into the rear end of a truck with mass M = 9000 kg moving in the same direction with speed Vi = 20.0 m/s. Immediately after the collision the car has a speed vf = 18.0 m/s in its original direction. a. What is the speed (m/s) of the truck immediately after the collision? b. How much mechanical energy (J) was lost as a result of the collision?