Two trains start simultaneously from opposite ends of a 140-km route and travel toward each other on parallel tracks. Train X, traveling at a constant rate, completes the 140-km trip in 4 hours. Train Y, travelling at a constant rate, completes the 140-km trip in 3 hours. How many kilometers had Train X traveled when it met Train Y?
Choose the correct option:
A) 60	B) 64	C) 68	D) 72	E) 76

Rationale: "if the two trains cover a total distance d , then train x travels ( 3 / 7 ) * d while train y travels ( 4 / 7 ) * d . if the trains travel 140 km to the meeting point , then train x travels ( 3 / 7 ) * 140 = 60 km . the answer is a ."
Answer: A