解:已知 P=9400-4Q,TC=4000+3000Q。TR=P×Q=(9400-4Q)Q=9400Q-4QMR=dTR/dQ=9400-8QMC=dTC/dQ=3000MR=MC 9400-8Q=3000Q=800 代入 P=9400-4Q:P=6200Tπ= TR-TC=(9400Q-4Q)-(4000+3000Q)=2556000