In what time will a railway train 56 m long moving at the rate of 39 kmph pass a telegraph post on its way? Answers:
A) 3 sec  B) 4 sec  C) 5 sec  D) 6 sec  E) 7 sec

Rationale: "t = 56 / 39 * 18 / 5 = 5 sec answer : c"
Answer: C