A coal-fired power plant can produce electricity at a variable cost of $0.07 per kilowatt-hour when running at its full capacity of 30 megawatts per hour, $0.16 per kilowatt-hour when running at 20 megawatts per hour, and $0.24 per kilowatt-hour when running at 10 megawatts per hour. A gas-fired power plant can produce electricity at a variable cost of $0.12 per kilowatt-hour at any capacity from 1 megawatt per hour to its full capacity of 5 megawatts per hour. The cost of constructing a coal-fired plant is $70 million, but it costs only $14 million to build a gas-fired plant. Required:
a. Consider a city that has a peak afternoon demand of 80 megawatts of electricity. If it wants all plants to operate at full capacity, what combination of coal-fired plants and gas-fired plants would minimize construction costs?
b. How much will the city spend on building that combination of plants?
c. What will the average cost per kilowatt-hour be if you average over all 80 megawatts that are produced by that combination of plants?