; (3) specify a mitigation fee in an amount the Secretary determines is sufficient to reasonably compensate, through habitat restoration or other appropriate measures, for any incidental take of migratory birds that results from such commercial activity; and (4) specify a permit fee in an amount that the Secretary determines is sufficient to offset the cost of developing and revising such regulations and administering the research program established under subsection (s). (c) Revision of general permits The Secretary shall revise a general permit issued under subsection (b) if such Secretary determines that revision is appropriate, or if— (1) the extent or nature of the incidental take of migratory birds caused by the commercial activity covered by the regulation is significantly different than the extent or nature of such incidental take that formed the basis of the regulation; (2) new best management practices or technologies can significantly reduce such incidental take and can practicably be adopted by the persons engaged in such commercial activity