§ 539. Powers of the comptroller. Whenever the state and the funds of which the comptroller is custodian or trustee, or any of them, shall be the owner of any bonds or notes of the authority the comptroller is hereby authorized as to any of such bonds or notes: (a) by agreement with the authority to modify the terms of such bonds or notes or the terms of any contract affecting or securing such bonds or notes, provided that no such agreement shall reduce the principal amount of such bonds or notes or in the opinion of the comptroller jeopardize the payment of the principal thereof or the interest thereon at the rate thereafter payable thereon and provided that any agreement relating to toll rates shall be approved by the commissioner; (b) to sell such bonds or notes to the authority at a price not less than the principal amount thereof and accrued interest; (c) to surrender such bonds or notes to the authority in exchange for other bonds or notes of the authority in a principal amount not less than the principal amount of the bonds or notes surrendered, with such cash adjustments as the comptroller may deem proper; (d) to make such agreements and to do such acts and things as the comptroller shall deem necessary or convenient to exercise the powers hereby conferred; provided, however, that nothing done under the provisions of this section shall in any manner affect the rights of other bondholders or noteholders.