In a town, there is 'n' number of people who go to office by different means. 60% of them go by buses, and the rest of them go by pooling cab. 70% of the people who go by bus return by scooters, and 20% of the people who go by pooling cab return by scooters. If the rest of them i.e 8000 people return by train, then find the value of 'n'.