a method or methods for computing the minimum price at which a member thereof may purchase from any investment company any redeemable security issued by such company and the maximum price at which a member may sell to such company any redeemable security issued by it or which he may receive for such security upon redemption, so that the price in each case will bear such relation to the current net asset value of such security computed as of such time as the rules may prescribe; and

a minimum period of time which must elapse after the sale or issue of such security before any resale to such company by a member or its redemption upon surrender by a member;

Such a securities association may also, by rules adopted and in effect in accordance with section 78o

–3 of this title, and notwithstanding the provisions of subsection (b)(6) thereof but subject to all other provisions of said section applicable to the rules of such an association, prohibit its members from purchasing, in connection with a primary distribution of redeemable securities of which any registered investment company is the issuer, any such security from the issuer or from any principal underwriter except at a price equal to the price at which such security is then offered to the public less a commission, discount, or spread which is computed in conformity with a method or methods, and within such limitations as to the relation thereof to said public offering price, as such rules may prescribe in order that the price at which such security is offered or sold to the public shall not include an excessive sales load but shall allow for reasonable compensation for sales personnel, broker-dealers, and underwriters, and for reasonable sales loads to investors. The Commission shall on application or otherwise, if it appears that smaller companies are subject to relatively higher operating costs, make due allowance therefor by granting any such company or class of companies appropriate qualified exemptions from the provisions of this section.

At any time after the expiration of eighteen months from December 14, 1970 (or, if earlier, after a securities association has adopted for purposes of paragraph (1) any rule respecting excessive sales loads), the Commission may alter or supplement the rules of any securities association as may be necessary to effectuate the purposes of this subsection in the manner provided by section 78s(c) of this title.

If any provision of this subsection is in conflict with any provision of any law of the United States in effect on December 14, 1970, the provisions of this subsection shall prevail.

for any period (A) during which the New York Stock Exchange is closed other than customary week-end and holiday closings or (B) during which trading on the New York Stock Exchange is restricted;

for any period during which an emergency exists as a result of which (A) disposal by the company of securities owned by it is not reasonably practicable or (B) it is not reasonably practicable for such company fairly to determine the value of its net assets; or

for such other periods as the Commission may by order permit for the protection of security holders of the company.