Anna begins jogging at a steady 3 m/sec down the middle of lane one of a straight track. Elsa starts even with her in the center of lane two but moves at 5 m/sec. At the instant they begin, Olaf is located 45 meters down the track in lane four, and is heading towards them in his lane at 6 m/sec. After how many seconds will the runners lie in a straight line?
