“underwriting period” means, for an entity acting as an underwriter of securities, the period commencing from the date of execution of an underwriting agreement or commitment until
(a) for securities acquired by the entity upon the exercise of an over-allotment option, four business days after the acquisition of those securities, and
(b) for all other securities, the earlier of
(i) the expiration of 40 days after the date of the closing of the purchase of the securities, and
(ii) the date of the completion of the distribution by the underwriter of the securities.