Three vehicles, A, B, and C, go from A to B at a certain speed. B starts 10 minutes later than A. B catches up with A by 50 minutes. C starts 10 minutes later than B. C catches up with B by 240 minutes. Let C start How many minutes to catch up with armor?
甲乙丙三辆车以一定的速度从A地到B地去，乙比甲晚出发10分钟，乙出发50分追上甲，丙比乙晚出发10分钟，240分追上乙，问丙出发多少分钟追上甲？
<result>80</result>