Notwithstanding the provisions of any lease to the contrary, for any lease or leases or well or wells identified by the Secretary and the State concerned pursuant to subsection (a), the Secretary is authorized to accept a prepayment for royalties in lieu of monthly royalty payments under the lease for the remainder of the lease term if the affected lessee so agrees. Any prepayment agreed to by the Secretary, State concerned and lessee which is less than an average $500 per month in total royalties shall be effectuated under this section not earlier than two years after August 13, 1996, and, any prepayment which is greater than an average $500 per month in total royalties shall be effectuated under this section not earlier than three years after August 13, 1996. The Secretary and the State concerned may condition their acceptance of the prepayment authorized under this section on the lessee’s agreeing to such terms and conditions as the Secretary and the State concerned deem appropriate and consistent with the purposes of this chapter. Such terms may—