; and (B) the standards required by each of subparagraphs (B) through (D) of paragraph (1) by not later than 2 years before the respective standard goes into effect. (3) Technological or economic feasibility (A) In general If the Administrator determines that a reduction in carbon intensity required under paragraph (1) is not technologically or economically feasible by the applicable deadline under such paragraph, the Administrator, in lieu of promulgating the standard otherwise required by paragraph (1), shall promulgate a standard that will achieve the maximum reduction in the carbon intensity of the fuel used by vessels on covered voyages that is technologically and economically feasible by such applicable deadline. (B) Considerations In determining technological and economic feasibility for purposes of subparagraph (A), the Administrator shall take into account the net reduction of emissions of greenhouse gases and potential adverse impacts on public health, safety, and the environment, including with respect to air quality, water quality, and the generation and disposal of solid waste. (4) Harmonization with international standards If the Administrator determines that standards mandated by the International Maritime Organization for reduction of the carbon intensity of fuel used by vessels for a calendar year are equally or more stringent than the standards under paragraph (1) for such calendar year, the Administrator may adopt such standards. (5) Exemption Any vessel that is on covered voyages for 30 days or fewer during a calendar year shall be exempt from the standards promulgated under this subsection for that year. (6) Common ownership or control For purposes of determining compliance with any standard established under this subsection, the Administrator may allow the carbon intensity of the fuels used by vessels under common ownership or control to be averaged. (7) Overcompliance The Administrator may allow vessels to credit overcompliance with any standard established under this subsection towards