Oil Blending: An oil company produces three brands of oil: Regular, Multi-grade, and Supreme. Each brand of oil is composed of one or more of four crude stocks, each having a different lubrication index. The relevant data concerning the crude stocks are as follows:

Crude Stock Lubrication Index Cost (S/barre/j Supp/y per day (barre/5) 1 20 7.10 1000 2 40 8.50 1100 3 30 7.70 1200 4 55 9.00 1100 Each brand of oil must meet a minimum standard for a lubrication index, and each brand thus sells at a different price. The relevant data concerning the three brands of oil are as follows: Brand Min. Lubrication Index Selling Price (Slbarrel) Daily Demand (barrels) Regular Multigrade Supreme