Problem: 7 Production of a certain chemical mixture should contain 80 mg. chlorides, 28 mg. nitrates and 36 mg. of sulphate. The company can use two substances. Substances P contain 8 mg. chlorides, 4 mg. nitrates and 6 mg. of sulphate per gallon. Substance Q contains 10 mg. chlorides, 2 mg. nitrates and 2 mg. of sulphate per gallon. Both substances cost tk.20 per gram. a. It is required to produce the mixture using substances P and Q so that the cost is minimized. b. Identify and calculate the surplus/slack. solution