An energy-efficient lightbulb, taking in 23.0 W of power, can
produce the same level of brightness as a conventional lightbulb
operating at power 100 W. The lifetime of the energy-efficient bulb
is 10 000 h and its purchase price is $4.80, whereas the
conventional bulb has lifetime 750 h and costs $0.56 per bulb.
Determine the total savings obtained by using one energy-efficient
bulb over its lifetime as opposed to using conventional bulbs over
the same time period. Assume an energy cost of $0.20 per
kilowatt-hour.