(a)   The city manager shall be the chief administrative officer of the city government, in conformity with the provisions of this charter.  He shall be selected by the council on the basis of training and ability alone, and need not be a resident of the city.  He shall serve at the pleasure of, and be subject to removal by the council, but he shall not be removed from office during a period of ninety (90) days following any regular city election except by the affirmative vote of five (5) members of the council.
   (b)   The council shall appoint a city manager within one hundred and twenty (120) days after any vacancy exists in such position, or they may appoint an acting manager during the period of a vacancy in the office, or the city manager, with the consent and approval of the council, may designate an administrative officer or employee of the city to act as city manager if he is temporarily absent from the city or unable to perform the duties of his office.