1.AB, XA = 1000 - 2 PA + PB; X = 1500 + >PA -1.5 PB XA,X() P4.A.B ,PA=?,PB=? (10%) Pa,B(10%) 1. "Aliang Store" sells two commodities A and B, and their demand functions are XA1000-2Pa +Pb; Xb=1500+2Pa-1.5Pb Among them, XaXb are respectively the units sold (pieces) PA. The members are the unit prices of the two commodities A and Find the Pa=?Pb=? (10%) that maximizes the total income. It is necessary to use the second-order partial derivative test method, indicating that you have calculated B, respectively, Pa, and B is the maximum (70%)