21. A cube has a certain volume. If the length of each side is quadrupled, by what factor will the volume increase? 22. An energy-efficient bulb claims to have the brightness of a 75-Watt bulb, but only uses 15-watt 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 on it? b) A kilowatt is 1,000 watts. The kilowaii-hour is a common unii for energy, obiained by multiplying the power in kilowatts by the time used in hours. How many kilowatt- hours (kWh) will you use when burning the 75-watt bulb for the year? c) How many kilowatt-hours (kWh) will you use when burning the 15-watt bulb for the year? d) Assuming that the cost of electricity is 15% per kWh, what is the cost of using the 75 W bulb for the year? P e) Assuming this same cost, what is the cost of using 15W bulb for the year? f) How much do you save per year by using the 15W bulb? g) How much would you save every year if you replaced 20 of the 75W bulbs with the 15W bulbs?