The Energy and Environment Minister has asked you to advise her on promoting "green power." She has been given a proposal to offer a 1/c per kWh subsidy to green power. You suggest that she should instead impose a carbon tax which roughly equates to a 1/c per kWh tax on polluting plants. She says that the cost advantage of green power is the same either way, but taxes are harder to sell politically. You still argue for the tax. Why