The ratio of the speed of boats ‘A’ and ‘B’ in still water is 8:9, respectively. The speed of the current is 25% of the speed of boat ‘A’ in still water. If boat ‘A’ takes 7.5 hours to travel 750 km downstream, then find the time taken by boat ‘B’ to travel 210 km upstream and 330 km downstream. (Note: Both the boats are rowing in the same stream.)