725.1.5. For the purposes of the definition of “qualified corporation” in section 725.1.3, the assets of a corporation that is associated in a taxation year with one or more other corporations are equal to the amount by which the aggregate of the assets of the corporation and those of each corporation associated with it, determined in accordance with that definition and section 725.1.4, exceeds the aggregate of the amount of investments the corporations own in each other and the balance of accounts between the corporations.