There are three circular runways, the centers of which are all at the flagpoles in the playground. The length of the inner circle runway is (1/6) km, the length of the middle circle runway is (1/5) km, and the length of the outer circle runway is (3/8) km. A, B, and C run in the same direction in the inner circle, middle circle, and outer circle respectively. At the beginning, all three people are in the due east direction of the flagpole. A runs 3.5 kilometers per hour, and B runs 3,000 kilometers per hour. M, C runs 5 kilometers per hour. They set off at the same time. I would like to ask: How many hours later, the three returned to the starting point at the same time for the first time?
三条圆形跑道，圆心都在操场中的旗杆处．里圈跑道长(1/6)千米，中圈跑道长(1/5)千米，外圈跑道长(3/8)千米．甲、乙、丙三人分别在里圈、中圈、外圈沿同样的方向跑步，开始时，三人都在旗杆的正东方向，甲每小时跑3.5千米，乙每小时跑3千米，丙每小时跑5千米．他们同时出发．请问：几小时后，三人第一次同时回到出发点？
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