(2) General definitions. The following definitions are applicable to the numerator and

81-03-09-20. (2) General definitions. The following definitions are applicable to the numerator and denominator of the property factor, as well as other apportionment factor descriptions: (a) "Average value" of property means the amount determined by averaging the values at the beginning and end of the income tax year, but the tax commissioner may require the averaging of monthly values during the income year or such averaging as is necessary to reflect properly the average value of the trucking company's property, in accordance with North Dakota Century Code section 57-38.1-12 and article IV(12) of North Dakota Century Code section 57-59-01 and section 81-03-09-21. (b) "Mobile property" means all motor vehicles, including trailers, engaged directly in the movement of tangible personal property. (c) "Mobile property mile" is the movement of a unit of mobile property a distance of one mile whether loaded or unloaded. 27 (d) "Original cost" is deemed to be the basis of the property for federal income tax purposes prior to any federal income tax adjustments, except for subsequent capital additions, improvements thereto, or partial dispositions, or, if the property has no such basis, the valuation of such property for interstate commerce commission purposes. If the original cost of property is ascertainable under the foregoing valuation standards, the property is included in the property factor at its fair market value as of the date of acquisition by the taxpayer in accordance with section 81-03-09-19. (e) "Property used during the course of the income year" includes property which is available for use in the taxpayer's trade or business during the income year. (f) "Purchased transportation" means the taxpayer's use of a motor vehicle owned and operated by another for the purpose of transporting tangible personal property for which a charge, whether based upon a per diem, mileage, or other basis is incurred. (g) The "value" of owned real and tangible personal property means its original cost, in accordance with North Dakota Century Code section 57-38.1-11 and article IV(11) of North Dakota Century Code section 57-59-01 and section