A farmer that owns a wind turbine realizes that energy generated during the night is wasted and builds a pumped-up storage dam. He builds two identical water reservoirs whose elevations differ by 10 metres. Each reservoir has dimensions of 40 metres length, 36 metres width and 2 metres depth. Supposing that the pumped-up storage has 100% efficiency, how many kWh of wind energy can be stored in it? Hint: First find the potential energy in Joules using the gravitational acceleration constant 10 metres/squaresecond and water density of 1,000 kgs per cubicmetre.