If an environmental agency is charging polluters a tax to reduce their level of pollution down to the optimal level, what level of tax will be required to achieve that outcome? Question 12Answer a. A tax per unit of pollution equal to the marginal benefit at the social optimum b. A tax per unit of pollution equal to the average cost of pollution at zero abatement c. A tax per unit of pollution equal to the present value of all future costs from pollution d. A tax per unit of pollution of abatement equal to the marginal cost of pollution at zero pollution