The City Manager may designate, by letter filed with the Clerk and President of Council, any qualified administrative officer of the Municipality to perform the duties of the City Manager during a disability or specific period of absence. The person so designated shall have during such period such power and authority of the City Manager as is necessary and appropriate. Council may, by resolution, alter or amend the designation made by the City Manager or may appoint a qualified administrative officer of the Municipality to perform such duties in the event that the Manager does not make a designation as provided herein.