完全竞争市场均衡条件：MR=MC=AR=AC=P=d
MR=（QD*P）′=（50000P-2000P²）′=50000-4000P ①
MC=(QS*P）′=（40000P+3000P²）′=40000+6000P ②
MR=MC→①=②→P=10=d