A power plant burns coal, oil, and gas to produce electricity. Each ton of coal generates 600-kilowatt hours, emits 20 units of sulfur dioxide and 15 units of particulate matter, and costs $200. Each ton of oil generates 550-kilowatt hours, emits 18 units of sulfur dioxide and 12 units of particulate matter, and costs $220. Finally, each ton of coal generates 500-kilowatt hours, emits 15 units of sulfur dioxide and 10 units of particulate matter, and costs $250. The environmental protection agency restricts the daily emission of sulfur dioxide to no more than 60 units and the daily emission of particulate matter to no more than 75 units. The power plant wants to spend no more than $2000 a day on fuel. We wish to determine how much fuel of each type the power plant should use in order to maximize the amount of energy produced.