Explanation:
Bus A leave depot at = 3pm
Bus B leave depot at = 3 pm
both leave depot at 3 pm so
Bus A complete its route in25 mins
Bus A reach at his point at 3:25 pm
Bus B complete its route in 30 mins
Bus B reach at his point at 3:30 pm
So
If the buses go back to depot it will take 25 mins so Bus A reach back at depot at 3:50 pm
Bus B at 4:00 pm