Water over the Dam

Approximately 5.7x10^6 kg of water fall 50 m over Niagara Falls each second.

(a) What is the decrease in the gravitational potential energy of the water-Earth system each second?

(b) If all this energy could be converted to electrical energy by an electric generating plant (it cannot be), at what rate would electrical energy by supplied? (The mass of 1 m^3 of water is 1000 kg.)

(c) If the electrical energy were sold at 5 cents/kW · h, what would be the yearly cost?