How much time will a train of length 420 m moving at a speed of 72 kmph take to cross another train of length 640 m, moving at 36 kmph in the same direction?  Choose the correct option.
A) 50 B) 99 C) 88 D) 76 E) 106

Rationale: "the distance to be covered = sum of their lengths = 420 + 640 = 1060 m . relative speed = 72 - 36 = 36 kmph = 36 * 5 / 18 = 10 mps . time required = d / s = 1060 / 10 = 106 sec . answer : e"
Answer: E