An express train travelled at an average speed of 100 km/hr, stopping for 3 minutes after every 75 km. how long is it take to reach its destination 600 km from the starting point? `6\ h r s\ 21\ m in` b. `6\ h r s\ 24\ m in` c. `6\ h r s\ 27\ m in` d. `\ 6\ h r s\ 30\ m in`