(1) Pursuant to 77-1-905(2), MCA, the department will set the minimum annual rent for any commercial lease to obtain the full market value of that lease. Such rental shall be at a rate not less than the product of the appraised value of the land multiplied by a rate that is two percentage points a year less than the current federally-guaranteed, annual, 20-year bond rate provided by the Montana Board of Investments commercial loan rate sheet. For the purpose of calculating the minimum annual rent, the department may round the 20-year rate to the nearest whole number.