In a portfolio problem, X1, X2, and X3 represent the number of shares purchased of stocks 1. 2, and 3, which have selling prices of $15, $47.25, and $110, respectively. The investor has up to $50,000 to invest. The expected returns on investment of the three stocks are 8%, 6%, and 11%. An appropriate objective function is: 1) MAX.08(15)X1 +06(47.25)X2 +.11(110)X3 2) MAX.08x1 +.06X2 +.11X3 3) MAX.06(15)X1 +.08(47.25)X2 +.11(110)X3 4) MAX 15X1+ 47.25X2 +110x3