(1) When imputing value pursuant to 15-35-107, MCA, the department may use valuation methods which approximate the value of the coal, including but not limited to comparable actual arm's-length sales, comparable actual arm's-length sales adjusted to FOB mine price, or published coal sales indexes. Contract term, tonnage, quality, Btu rating, and any other appropriate comparability criteria will be considered.

(2) If using comparable sales in computing value, the department will maintain the confidentiality of all comparable contract data and will use contract data provided by the producer in question whenever possible.