If the Mayor is temporarily unable to perform the duties of his office, the mayor’s designated officer whose appointment has been confirmed by the Common Council shall act as Mayor until the Mayor is able to. The designation must be in writing and filed with the city clerk. If the Mayor has not made such a designation, the president of the Common Council shall perform the Mayor’s duties until the Mayor is able to. If the office of Mayor is vacant (as a result of resignation, removal, death or permanent inability to perform duties of the office of mayor) the president of the Common Council shall serve the balance of the term.