A single-track railway has a total length of 240 kilometers, and there is a meeting station every 20 kilometers (when two cars meet, one car stops at the meeting station, and the other car can pass through). Two trains, A and B, depart from both ends at the same time. A train travels 75 kilometers per hour, and train B travels 45 kilometers per hour. In order to ensure that the express train runs on time, the slow train should give way to the express train. In order to keep the waiting time as short as possible, at which station should car B wait for car A to pass after departure?
一条单线铁路全长240千米，每隔20千米有一个会车站(当两车相遇时，一车停在会车站内，另一车可通过)．甲、乙两列火车同时从两端出发，甲车每小时行75千米，乙车每小时行45千米．为保证快车正点运行，慢车应给快车让路．为使等候时间尽量短，乙车应在出发后的第几个会车站等候甲车通过？
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