From point P, at 6 : 30 pm, a train starts moving towards Q with the speed of 40 km/hr. Another train starts moving from point Q at 7:30 p.m. towards point P at the speed of 60 km/hr. Both of them meet at 11:30 p.m. at point R. What is the ratio of PR and QR?

Options

A. A) `3:4`
B. B) `5:6`
C. C) `4:5`
D. D) `5:4`