Problem Solving

A train of length 600 m is leaving a platform at 15 kmph. Before it completely left the platform, another train of length 300 m coming in the opposite direction with a speed of 75 kmph starts crossing the first train. The second train entered the platform completely, and simultaneously crossed the first train. If the length of the platform is 1,125 metres, then what is the time taken by the second train to cross the platform after it has crossed the first train?

1 kmph = 5/18 m/sec; 1 km = 1000 m, m for meters and sec for seconds.
kmph stands for km per hour.
A. 72 seconds
B. 60 seconds
C. 54 seconds
D. 48 seconds
E. 36 seconds

OA C if not badly worded, I hope