In addition to the City Manager, and subordinate to him in the performance of the duties of their several offices, except the Clerk, Treasurer and City Attorney insofar as their duties as clerk and treasurer of, and attorney for the Commission are concerned, the administrative officers of the City shall be the Clerk, the Treasurer, the Assessor, the City Attorney, the Police Chief, the Fire Chief, the Health Officer, the Ambulance Director and other officers included in the administrative plan approved by the Commission.