How long does a train 125 m long running at the speed of 78 km/hr takes to cross a bridge 125 m length?	Choose the correct choice from the following answers:
A) 12.7 sec B) 10.1 sec C) 11.5 sec D) 12.1 sec E) 11.7 sec

Rationale: "speed = 78 * 5 / 18 = 21.7 m / sec total distance covered = 125 + 125 = 250 m . required time = 250 / 21.7 ' = 11.5 sec . answer : c"
Answer: C