If two trains are 120 miles apart and are traveling toward each other

If two trains are 120 miles apart and are traveling toward each other at constant rate of 30 miles per hour and 40 miles per hour, respectively, how far apart will they be 1 hour before they meet? (A) 10 (B) 30 (C) 40 (D) 50 (E) 70 [Reveal] Spoiler: As the question ask how far apart they will (...)