Upon receiving an initiatory or referendary petition from the clerk the council shall, within thirty (30) days, unless otherwise provided by law, either,
(a) Adopt the ordinance as submitted by initiatory petition;
(b) Repeal the ordinance, or part thereof, referred to by a referendary petition or;
(c) Determine to submit the proposal provided for in the petition to the electors.
(d) When the provisions of this charter require the council to submit the proposal to the electors, it shall be submitted at the next election held in the city for any other purpose, or in the discretion of the council, at a special election. In any event, it shall be submitted at an election where there is sufficient time for the processing of the notice of registration and of election and providing for absentee ballots. The results shall be determined by a majority vote of the electors voting thereon, except in cases where otherwise required by law.