Two racing cars A and B are at rest alongside each other at a point O on a straight horizontal test track. The mass of A is 1200 kg. The engine of A produces a constant driving force of 4500 N. When A arrives at a point P its speed is 25 m/s. The distance OP is d m. The work done against the resistance force experienced by A between O and P is 75000 J.

1. Show that d = 100.
2. Car B starts off at the same instant as car A. The two cars arrive at P simultaneously and with the same speed. The engine of B produces a driving force of 3200 N and the car experiences a constant resistance to motion of 1200 N.
3. Find the mass of B.
4. Find the steady speed which B can maintain when its engine is working at the same rate as it is at P.