Large fossil fuel or nuclear electrical power plants operate most economically when run at full capacity 24 hours a day. Excess electrical energy can be "stored" and recovered by pumping water into a reservoir on top of a mountain and letting it fall through turbines during periods of peak demands. At such a facility, the water falls an average distance of 250 m. The reservoir has a surface area of 1.3 km^2 and a depth averaging 10m.
a.) how much energy is available each time the reservoir is emptied?
b.) if it is emptied over a period of 10 hours, and 80 percent of the energy is converted into electrical energy, what is the power generated?