Section 71. A majority of the members of the city council shall constitute a quorum. Except as otherwise authorized by section twenty-three A of chapter thirty-nine, all meetings of the city council shall be public; and the mayor, if present, shall preside and may vote. In the absence of the mayor the president of the city council shall preside, and in the absence of both, a temporary chairman shall be chosen. The city clerk shall be, ex officio, clerk of the city council, and shall keep records of its proceedings; but in case of his temporary absence, or of a vacancy in the office, the city council may elect by ballot a temporary clerk, who shall be sworn to the faithful discharge of his duties and may act as clerk of the city council until a city clerk is qualified. All final votes of the city council involving the expenditure of fifty dollars or more shall be by yeas and nays and be entered upon the records. On the request of one member any vote shall be by yeas and nays and be entered upon the records. The affirmative vote of at least three members shall be necessary for the passage of any order, ordinance, resolution or vote.