— I think it was his excitement for his success in the first half that led to his eventual failure in the game.

— You bet. Old sayings never fail, “________”

A．Failure is the mother of success

B．Pride goes before a fall

C．A hero is nothing but a product of his time

D．A fall into the pit, a gain in the wit

假设在完全竞争行业中有许多相同的厂商，代表性厂商LAC曲线的最低点的值为6美元，产量为500单位；当工厂产量为550单位的产品时，各厂商的SAC为7美元；而且知道市场需求函数与供给函数分别为：Q_d=80 000-5 000P，Q_s=35 000+2 500P。
(1)求市场均衡价格，并判断该行业是长期还是在短期处于均衡，为什么
(2)在长期均衡时，该行业有多少家厂商
(3)如果市场需求函数发生变动，变为

=95 000-5 000P，试求行业和厂商的新的短期均衡价格及产量，厂商在新的均衡点上，盈亏状况如何