1. Extension of retained use estate (a) Extension required Not later than 90 days after a request by the grantor, the Secretary of the Interior shall extend the retained use estate in accordance with this section. (b) Requirements The extension under subsection (a) shall— (1) except as provided in paragraph (2), be effective for the 60-year period beginning on the date the retained use estate would, but for the extension under this section, expire; (2) be subject to the terms of the retained use estate, including the right of the grantor to terminate the retained use estate in accordance with the terms thereof; and (3) require the grantor to pay to the United States, in quarterly installments for the period of the extension, fair market value rental in an amount equal to— (A) for each of the first 15 years of the extension, 1.2 percent of the gross revenues of the resort in accordance with subsection (c); and (B) for each year of the extension thereafter, the amount determined under subparagraph (A), except that— (i) such amount shall be adjusted if requested by the Secretary or the grantor; (ii) any such adjustment shall be determined— (I) through an agreement between the Secretary and the grantor; or (II) if the Secretary and the grantor are unable to agree on such an adjustment after a 60-day period for negotiation (or a longer period for negotiation agreed upon by the Secretary and the grantor), through binding arbitration between the Secretary and the grantor using the arbitration procedures specified in section 51.51 of title 36, Code of Federal Regulations; (iii) such adjustment shall take into account any amounts expended or to be expended by the grantor for preservation, maintenance, restoration, improvement, or repair and related expenses specified in section 102102(d)(2) of title 54, United States Code, to the extent such amounts are for the resort