2. A car of mass m travelling down the motorway at 100 km/hr suddenly stops pressing the accelerator pedal. The result is that the car slows to 60 km/hr in ten seconds. Suppose all travel is along a level road. (a) What is the average force acting on the car serving to slow it's motion? (b) How much power is required to maintain the car at 100 km/hr given this external force? (c) How much more energy is done in travelling at 105 km/hr than 100 km/hr? To how much petrol might this correspond?