Jack is trying to determine how he can save money by cutting his electricity bill. He is currently on a standard use plan for electricity and pays 7. 5 cents per kwh. He keeps track of when he uses electricity and is thinking about switching to an interval use plan for electricity which costs 3 cents per kwh for off-peak use and 15 cents per kwh for on-peak use. Off-peak hours are from 8pm - 8am and on-peak hours are from 8am - 8pm. Below is the chart of his electricity usage:.