((a)) ** .—** For each of model years 1993 through 2019 for each category of automobile (except an electric automobile or, beginning with model year 2016, an alternative fueled automobile that uses a fuel described in subparagraph (E) of section 32901(a)(1)), the maximum increase in average fuel economy for a manufacturer attributable to dual fueled automobiles is—

((1)) 1.2 miles a gallon for each of model years 1993 through 2014;

((2)) 1.0 miles per gallon for model year 2015;

((3)) 0.8 miles per gallon for model year 2016;

((4)) 0.6 miles per gallon for model year 2017;

((5)) 0.4 miles per gallon for model year 2018;

((6)) 0.2 miles per gallon for model year 2019; and

((7)) 0 miles per gallon for model years after 2019.

((b)) ** .—** In applying subsection (a), the Administrator of the Environmental Protection Agency shall determine the increase in a manufacturer’s average fuel economy attributable to dual fueled automobiles by subtracting from the manufacturer’s average fuel economy calculated under section 32905(f) the number equal to what the manufacturer’s average fuel economy would be if it were calculated by the formula under section 32904(a)(1) by including as the denominator for each model of dual fueled automobiles the fuel economy when the automobiles are operated on gasoline or diesel fuel.