(1) In general, all revenues derived from transactions and activities in the regular course of the taxpayer's trade or business which produces apportionable income shall be included in the denominator of the receipts factor as provided in ARM 42.26.253.

(2) The numerator of the receipts factor is the total revenue of the taxpayer in this state during the income year. The total state revenue of the taxpayer, other than revenue from hauling freight, mail, and express, shall be attributable to this state in accordance with ARM 42.26.254 through 42.26.259.

(3) Numerator of the receipts factor from freight, mail, and express. The total revenue of the taxpayer attributable to this state during this income year from hauling freight, mail, and express shall be:

(a) Intrastate - all receipts from any shipment which both originates and terminates within this state; and

(b) Interstate - that portion of the receipts from movements or shipments passing through, into or out of this state as determined by the ratio which the mobile property miles traveled by such movements or shipments in this state bear to the total mobile property miles traveled by movements or shipments from points of origin to destination.