Yet,the average reclamation cost for a surface coal mine being reclaimed today isonly four dollars per ton of coal that the mine produced, less than half what it cost to reclaim surface mines in the years immediately after the regulation stook effect.
请问NN,斜体字那句话是作为adjective modifier修饰subject (the average reclamation cost)还是object(four dollars)。或者是作为adverbial modifier修饰主句的?