A train consists of a 60 Mg engine and three cars, each having a mass of 25 Mg . If it takes 90 s for the train to increase its speed uniformly to 45 km/h , starting from rest, determine the force T , developed at the coupling between the engine E and the first car A . The wheels of the engine provide a resultant frictional tractive force F which gives the train forward motion, whereas the car wheels roll freely. Also, determine F, acting on the engine wheels.