Question

CFL light bulbs consume less power than their incandescent counterparts while providing about the same amount of light. Suppose a CFL, while consuming only 20 Watts of power produces as much light as a 60 Watt incandescent bulb. Also, suppose a house has 8 lightbulbs which are all replaced by CFL bulbs and, on average, all the bulbs are on 4.6 hours per day (or night). If electricity costs 9 cents/kwh, how much money is saved over the course of 8 years when switching to CFL bulbs in dollars?