6 A refinery manufactures two grades of jet fuel, F1 and F2, by blending four types of gasoline, A, B, C, and D. Fuel F1 uses gasolines A, B, C, and

D in the ratio 1:1:2:4, and fuel F2 uses the ratio 22:13. The supply limits for A, B, C, and D are 1000, 1200, 900, and 1500 bbl/day, respec- tively. The costs per bbl for gasolines A, B, C, and D are $120, $90, $100, and $150, respectively. Fuels F1 and F2 sell for $200 and $250 per bbl, respectively. The minimum demand for F1 and F2 is 200 and 400 bbl/day, respectively. Develop an LP model to determine the optimal production mix for F1 and 12-