A model steam engine of 1.00-kg mass pulls eight cars of 1.00-kg mass each. The cars start

Question:

A model steam engine of 1.00-kg mass pulls eight cars of 1.00-kg mass each. The cars start at rest and reach a velocity of 3.00 m/s in a time of 3.00 s while moving a distance of 4.50 m. During that time, the engine takes in 135 J of heat. What is the change in the internal energy of the engine?