A train travelling at 48 km/hr completely crosses another train having half its length and travelling in opposite direction at 42 km/hr, in 12 seconds. It also passes a railway platform in 45 seconds. The length of the platform is ________.
A 400 m
B 450 m
C 560 m
D 600 m
Rohan's house number is just before Mehak's house number. What is Mehak's house number ?