A locomotive of mass 6.00*10^4 kg is moving eastward by a speed of 10.8 km/h. It collides and couples with two coupled railroad cars, each mass 2.00*10^4 kg, moving westward on the same track by an initial speed of 5.40 km/h. What is the speed of the coupled system (locomotive and two railroad cars) after the collision? What is the direction of motion after the collision? How much energy is transformed into internal energy?