Two towns are connected by railway. Can you find the distance between them? I. The speed of the mail train is 12 km/hr more than that of an express train. II. A mail train takes 40 minutes less than an express train to cover the distance.

• A. I alone sufficient while II alone not sufficient to answer
• B. II alone sufficient while I alone not sufficient to answer
• C. Either I or II alone sufficient to answer
• D. Both I and II are not sufficient to answer
• E. Both I and II are necessary to answer