TC=12000+0.025Q^2=12000+0.025*(6750-50P)^2
利润=PQ-TC=P*(6750-50P)-[12000+0.025*(6750-50P)^2]
=6750P-50P^2-12000-6750^2/40+675000P/40-2500P^2/40
=（-4500P^2+945000P+46042500)/40
当价格P=945000/（4500×2）=105时,利润最高=2391375
产量Q=6750-50×105=1500