If, prior to the date when any ordinance shall take effect, a petition signed by qualified electors at least equal in number to ten percent of the entire vote cast at the last preceding general municipal election, shall be filed with the Clerk, protesting against the enactment of such ordinance, it shall be suspended from taking effect. Immediately upon the filing of the petition, the Clerk shall do all things required in section 11.2. (b) of this article. The Council shall then immediately reconsider such ordinance; and, if it does not entirely repeal the same, shall submit it to popular vote at the next municipal election; or the Council, in its discretion, may call a special election for that purpose; and such ordinance shall not take effect unless a majority of the qualified electors voting on the ordinance at such election shall vote in favor of the ordinance.