Electricity Rates in Illinois Commonwealth Edison Company supplies electricity to resident...

Electricity Rates in Illinois Commonwealth Edison Company supplies electricity to residential customers for a monthly customer charge of $7.58 plus 8.275 cents per kilowatt-hour for up to 400 kilowatt-hours.

(a) Write a linear model that relates the monthly charge C, in dollars, to the number x of kilowatt-hours used in a month, 0 ≤ x ≤ 400.

(b) Graph this equation.

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(c) What is the monthly charge for using 100 kilowatt-hours?

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(d) What is the monthly charge for using 300 kilowatt-hours?

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(e) Interpret the slope of the line.

Source: Commonwealth Edison Company, April 2006.