Two trains 300m and 400m long run at the speed of 36kmph and 18 kmph in opposite directions in parallel tracks. The time which they take to cross each other is?
Choose the correct answer:  A) 5.6 sec  B) 46.67 sec  C) 10.8 sec  D) 12.6 sec  E) 15 sec

Rationale: "relative speed = 36 + 18 = 54 kmph * 5 / 18 = 15 m / s distance covered in crossing each other = 300 + 400 = 700 m required time = 700 * 1 / 15 = 46.67 sec answer is b"
Answer: B