A person goes to office either by car, scooter, bus or train probability of which being 1/7, 3/7, 2/7 and 1/7 respectively. Probability that he reaches offices late. if he takes car, scooter, bus or train is 2/9, 1/9, 4/9 and 1/9 respectively. Given that he reached office in time, then what is the probability that he travelled by a car?