Assume the earth to be sphere of a uniform density, (a) what is its rotational energy? Take the radius of the earth to be 6,400km and the mass of the earth to be 6x10^24kg. (b) suppose that this energy could be harnessed for our use. For how long could the earth supply 1.0kw of power to each of the 4.2x10^9 persons on the earth?