An affirmative vote equal to a majority of the members of the Council not excused from voting on the issue (i.e., assuming no member is excused, three Council members) shall be required to adopt an ordinance, take any action having the effect of an ordinance, or make, ratify, or authorize any contract on behalf of the City. In addition, no ordinance nor any action having the effect of any ordinance may be finally adopted on the date on which it is introduced except by an affirmative vote equal to or greater than two-thirds of the actual membership of the Council (excluding vacant seats), unless the Council has first held a public hearing on the ordinance. Therefore, assuming no vacant seats, unless the Council first holds a public hearing on an ordinance, that ordinance may not be adopted on the date it is introduced except by an affirmative vote of four Council members. For purposes of this section, an ordinance shall be deemed to have been introduced on the date the subject matter is first voted on by the Council. This section does not modify G.S. § 159-17.