Any trust company qualified to act as fiduciary in this state may establish common trust funds (referred to in this regulation as "collective investment funds") for the purpose of furnishing investments to itself as fiduciary, or to itself and others, as co-fiduciaries; and may, as such fiduciary or co-fiduciary, invest funds which it lawfully holds for investment in interests in such common trust funds, if such investment is not prohibited by the instrument, judgment, decree, or order creating such fiduciary relationship, and if, in the case of co-fiduciaries, the trust company procures the consent of its co-fiduciary or co-fiduciaries to such investment, and provided such investment is not in contravention with the provisions of chapter 30.24 RCW:

(a) In a common trust fund maintained by the trust company exclusively for the collective investment and reinvestment of moneys contributed thereto by the trust company in its capacity as trustee, executor, administrator, or guardian.

(b) In a fund consisting solely of assets of retirement, pension, profit sharing, stock bonus or other trusts which are exempt from federal income taxation under the Internal Revenue Code.