(a) The eligible grant amount for each heavy-duty on-road vehicle being replaced is up to 80%, as determined by the executive director, of the total cost for replacement.(b) The eligible grant amount for each light-duty on-road vehicle being replaced is up to 80%, as determined by the executive director, of the total cost for replacement.(c) The executive director may establish more specific standards for determining grant amounts within the maximum percentage of total costs established under this section consistent with the priorities for project selection, including consideration of the federal emission standards for different model years of heavy-duty engines and light-duty vehicles, decisions on pollutants of concern, and other factors that will help implement the project priorities.(d) To be eligible for replacement, vehicles and engines imported into the United States from another country must have met all applicable emissions certification requirements for importation.