A). 1,000 watts = 1 kilowatt
5,000 watts = 5 kilowatts
b). (5 kilowatts) x (2 hours) = 10 kilowatt-hours (kWh)
c). (10 kWh) x (15 cents/kWh) = $1.50
Seven days after a waxing gibbous moon, the moon will be waning gibbous, and at some point during that seven days, it will have been Full.
Because it's the basis of how everything around you works
The amount of energy before and after any energy transformations remain the same because energy cannot be created or destroyed. From the law conservation of energy; any time energy is transferred between two objects, or converted from one form into another, no energy is created and none is destroyed. The total amount of energy involved in the process remains the same.