The distance between salem and trichy is 170 km. A bus starts from salem at 6 a.m. and travels towards trichy at 20 km/hr. Another bus starts from trichy at 7 a.m. and travels towards salem at 30 km/hr. At what time will they meet? a) 7a.m b) 8a.m c) 9a.m d) 10a.m