Jessica's parents are always telling her to turn off the lights when she leaves a room. A light bulb requires 75 watts to run when it is turned on. The fixture in Jessica's room requires four of these bulbs.
a. Jessica's parents estimate that she leaves the lights on unnecessarily for 2.5 hours per day. How many watt-hours of electricity are used by these bulbs during 2.5 hours?
b. Approximately how many kilowatt-hours of electricity are used in a year to keep these bulbs lit for 2.5 hours per day?
c. At a cost of $0.09 per kilowatt-hour, how much money is wasted per year by keeping these lights on unnecessarily? Round to the nearest dollar.
d. If five million teenagers keep lights on as Jessica does, how much is wasted in unnecessary electric expenses?