; (C) not later than 8 years after the date of enactment of this Act, requirements take effect to regulate sources which, collectively, emit not less than 75 percent of non-auction greenhouse gases emitted in the United States; and (D) not later than 10 years after the date of enactment of this Act, requirements take effect to regulate sources which, collectively, emit 100 percent of non-auction greenhouse gases emitted in the United States. (2) Baseline The percentages specified in paragraph (1) shall be applied relative to the aggregate quantity of non-auction greenhouse gases emitted in the United States during the calendar year in which the initial list under subsection (b)(1) is required to be finalized by such subsection. (e) Priorities In determining priorities for regulating the emissions of non-auction greenhouse gases under subsection (c), the Administrator shall consider— (1) the degree to which the gases involved contribute to global warming