78.712.  Council to consist of seven members, qualifications — term, vacancies, how filled — quorum. — 1.  If a city adopts the optional city manager form of government, the council shall consist of seven members, and all persons now eligible for the position of councilman under the laws governing cities of the third class shall be eligible to serve as councilmen under the provisions of sections 78.700 to 78.720, provided that a ward councilman must reside within the ward he represents.  One councilman shall be elected from each ward by the qualified voters thereof, and two councilmen shall be elected at large by the qualified voters of the city, at the first municipal election after the adoption of the optional form of government provided in sections 78.700 to 78.720.  The term of councilmen shall be three years; provided, that of the first council elected after the adoption of sections 78.700 to 78.720, the councilmen representing wards two and four shall serve terms of one year; the councilmen representing wards one and three shall serve terms of two years; and the councilman representing ward five, along with the two councilmen elected at large, shall serve terms of three years.  In any special election held to replace a councilman elected by the voters of a particular ward, only the voters of that ward shall be eligible to vote.

  2.  Four members of the council shall constitute a quorum to do business, and no action of the council shall be valid unless at least four shall vote in favor of such action.