Unleased Federal lands within a participating area are treated as follows:

(a) For royalty purposes only, you must allocate production to unleased Federal lands in the participating area as if the acreage were committed to the participating area.

(b) The unit operator is primarily liable for paying and must pay royalty to the United States for such allocated production based on a rate not less than the highest royalty rate for any Federal lease in the participating area. In the event the unit operator does not pay any royalties owed under this paragraph, each lessee of lands committed to the participating area is responsible for paying such royalties in the same proportion as that lessee's percentage of surface acreage within the participating area, excluding the unleased acreage.