U.S. carbon emissions fell in the past year as coal generation decreased by 19 percent and gas generation increased by 38 percent. A gas-fired plant produces half the CO2 emissions of a coal-fired one, but the use of shale gas is the subject of a heated environmental debate in which critics allege that it contaminated groundwater.
How does the switch from coal generation to gas generation change the external cost of and deadweight loss from generating electricity? Draw a graph to illustrate your answer.