The total electricity generation in the United States is 12.68 quads/year. The water used by the power sector was 136,000 MMgal/day. Calculate the amount of water used per kilowatt-hour of electricity. Note: 1 quad =10E15BTU=1.055E18 Joules =2.93E11kil watt-hours Certain renewable energy sources like wind or photovoltaic do not use any water outside of the manufacturing process. Considering the water energy nexus, comment on the result of your calculation in part (a)