City A to City B is a downstream journey on a stream which flows at a speed of 5km/hr. Boats P and Q run a shuttle

City A to City B is a downstream journey on a stream which flows at a speed of 5km/hr. Boats P and Q run a shuttle service between the two cities that are 300 kms apart. Boat P, which starts from City A has a still-water speed of 25km/hr, while boat Q, which starts from city B at the same time has a still-water speed of 15km/hr. When will the two boats meet for the first time? (this part is easy) When and where will they meet for the second time?

1. 7.5 hours and 15 hours
2. 7.5 hours and 18 hours
3. 8 hours and 18 hours
4. 7.5 hours and 20 hours

Ans: D.  7.5 hours and 20 hours