Whenever the board determines that the account created pursuant to section seven-a of this article contains a surplus above those amounts necessary to provide fully for the expected costs of claims and other expenses listed in subsection (a), section seven of this article, the plan may use such surpluses to subsidize the premium of enrollees with an annual average household income at or below four hundred percent of the federal poverty level. The board may propose emergency rules and shall propose rules for legislative approval in accordance with the provisions of article three, chapter twenty-nine-a of this code to establish eligibility criteria for enrollees who are eligible for premium subsidy pursuant to this section.