An energy-efficient bulb claims to have the brightness of a 75W bulb but only uses 15W of electrical power. 

a. If you have this light bulb on for 5 hours a day, for 350 days during a year, how many hours is it on? 

b. A kilowatt is 1000 watts. The kilowatt-hour is a common unit for energy, obtained by multiplying the power in kilowatts by the time used in hours. How many kilowatt-hours (kWh) will you use when burning the 75W bulb for the year? 

c. How many kilowatt-hours (kWh) will you use when burning the 15W bulb for the year? 

d. Assuming that the cost of electricity is 15¢ per kWh, what is the cost of using the 75W bulb for the year? e. Assuming this same cost, what is the cost of using the 15W bulb for the year? f. How much do you save by using the 15W bulb? 

g. How much would you save if you replaced 20 of the 75W bulbs with the 15W bulbs?