Two trains of equal length, running with the speeds of 60 and 40 kmph, take 40 seconds to cross each other while they are running in the same direction. What time will they take to cross each other if they are running in opposite directions?
Choose the correct choice from the following:
A) 10 sec
B) 16 sec
C) 13 sec
D) 67 sec
E) 8 sec

Rationale: "rs = 60 - 40 = 20 * 5 / 18 = 100 / 18 t = 40 d = 40 * 100 / 18 = 2000 / 9 rs = 60 + 40 = 100 * 5 / 18 t = 2000 / 9 * 18 / 500 = 8 sec answer : e"
Answer: E