7-4-18. Determination of sales in this state of other than tangible personal property for inclusion in sales factor.
Sales, other than sales of tangible personal property, are in this state if:
A. the income-producing activity is performed in this state; or
B. the income-producing activity is performed both in and outside this state and a greater proportion of the income-producing activity is performed in this state than in any other state, based on costs of performance.