4. A company has two electric power plants that supply the needs of three cities. Each power plant can supply the following numbers of kWh of electricity: plant 1,35 million; and plant 2, 50 million. The peak power demands in these cities as follows (in kWh): City 1, 40 million; City 2, 20 million; City 3 , 20 million. The costs of sending 1 million kWh of electricity from plant to city is given in the table below. To minimize the cost of meeting each city's peak power demand, represent the problem as a LP. Also indicate supply constraints and demand constraints