Please give solution step by step

/in /by

Please give solution step by step

Mona and Sona start simultaneously from two towns, P and Q, towards Q and P respectively at 8:00 a.m. R is a checkpost which is midway between P and Q. Both Mona and Sona turn back towards their respective starting points whenever they reach R and every time they reach their starting points they turn back and return to R. If the speeds of Mona and Sona are 45 km/hr and 60 km/hr respectively and PQ = 24 km, when will they reach R at the same time?