Light bulbs are rated by their power consumption in watts (W). Electricity is sold in units of energy, which is power multiplied by time. Electricity costs vary widely across the united states and are on the order of 0.06-0.23$/kw-hr for residential customers. Create a spreadsheet that utilizes electricity costs and the number of hours per day that a light bulbs is on as input variables. Then calculate the annual cost to operate a 60-W, 75-W, and 100-W incandescent bulb and a 15-W compact fluorescent bulb. Assuming the average household operates six 60-W, four 75-W, and two 100-W incandescent bulbs for 6 hours a dday. how much money can they save in year by changing all the bulbs to compact fluorescent?