A car leaves a starting point and drives at 60 km/hour. A second car leaves the same starting point some time later following the first car at a speed of 75 km/hour. It catches the first car after traveling a distance of 30 km. How many minutes later did the second car leave?
(A) 5 min. (B) 6 min. (C) 12 min. (D) 24 min. (E) None of these