An engineer works at a factory out os town. A car is sent for him from the factory every day and arrives at the railway station at the same time as the train. One day the engineer arrived at the station one our before his usual time and without waiting for the car, started walking towards factory. On his way he met the car and reached his factory `10` minutes before the usual time. For how much time (in minutes) did the engineer walk before the met the car ? (The car moves with the same speed everyday.)