These questions are based on the following information.
Three persons A, B and C start travelling from city P at 4:00 a.m., 5:00 a.m. and 6:00 a.m. respectively. All three reach the point q simultaneously and continue beyond that point. C reaches the point r first and turns back towards P. Thirty minutes after turning back, he crosses A.
If the distance between P and Q is equal to the distance between Q and R, then the time at which C crosses B for the second time is