An energy-efficient lightbulb, taking in p1 = W of power, can produce the same level of brightness as a conventional lightbulb operating at power W. The ifetime of the energy-efficient bulb is t1 = h and its purchase price is $, whereas the conventional bulb has a lifetime of h and costs $. Determine the total savings obtained by using one energy-efficient bulb over its lifetime as opposed to using conventional bulbs over the same time interval. Assume an energy cost of $ per kilowatt-hour