and B process the same number of parts at the same time. A processes 40 parts per hour. When A completes (1/2) of the task, B completes (1/2) of the task and there is still 40 parts left. This is the beginning of B. To improve work efficiency, it took another 7.5 hours to complete all processing tasks. At this time, A still has 20 parts left unfinished. Ask B to improve the work efficiency, how many parts are processed per hour.
甲、乙两人同时加工同样多的零件，甲每小时加工40个，当甲完成任务的(1/2)时，乙完成了任务的(1/2)还差40个，这是乙开始提高工作效率，又用了7.5小时完成了全部加工任务．这时甲还剩下20个零件没完成．求乙提高工效后，每小时加工零件多少个．
<result>8</result>