(a) In each lease other than a lease for coal and lignite executed under this subchapter, the lessor shall retain at least a one-eighth royalty.
(b) In a lease for coal and lignite executed under this subchapter, the lessor shall retain at least a royalty based on one of the following or a combination of the following:
(1) a sum certain per ton;
(2) a percentage certain of the gross sale price F.O.B. at the mine site of the coal and lignite; or
(3) a sum certain for each acre-foot of coal and lignite mined and removed from the premises.
(c) Royalties under a coal and lignite lease may be paid as advanced mineral royalties.