Qualified assets for purposes of section 901 include preferred stocks of any company organized under the laws of the United States, a state of the United States, the District of Columbia, Canada, or a province or territory of Canada, if the company has continuously and regularly paid the dividends provided for by the preferred stock during the 5 years preceding the investment; except that with respect to preferred stocks issued within the 5-year period, the dividend payments requirement applies only from the date of issuance, and in those cases the net earnings of the company and its subsidiaries available for fixed charges of the company and its subsidiaries and the net earnings of any predecessor organizations and their subsidiaries, if any, available for fixed charges of the predecessor organizations and their subsidiaries, must have averaged an amount per annum for the 5 fiscal years preceding the making of the investment at least equal to 2 times the total of the annual interest charges, including amortization of debt discount and expense, and dividends guaranteed, if any, and the preferred dividend requirement on a pro forma basis.