Question

A car of mass 1500 kg has a constant speed of 40 m/s when travelling up a hill inclined at sin a=1/15 to the horizontal with the engine’s power is 50 kW. The car moves down the same hill at the speed of 25 m/s while the engine working at 30kW. Find the acceleration of the car when it moves downhill if given resistance, R=v^2/k,
where k is a constant and v is the velocity of car.