A driver, having a definite reaction time, is capable of stopping over a distance of 30 m on seeing a red traffic light when speed of the car is 72 km/hr and over a distance of 10 m when the speed is 36 km/hr. Assuming that his reaction time and the acceleration of the car remain the same in all cases, find the distance over which he can stop the car when he is going at 54 km/hr.