All officers and employees of a city of the first class shall receive such compensation as the mayor and city council may fix at the time of their appointment or employment, subject to the limitations set forth in this section. The city council may at its discretion by ordinance combine and merge any elective or appointive office or employment or any combination of duties of any such offices or employments, except mayor and city council member, with any other elective or appointive office or employment so that one or more of such offices or employments or any combination of duties of any such offices or employments may be held by the same officer or employee at the same time. The city manager in a city under the city manager plan of government as provided in the City Manager Plan of Government Act may in his or her discretion combine and merge any elective or appointive office or employment or any combination of duties of any such offices or employments, except mayor and city council member, with any other elective or appointive office or employment so that one or more of such offices or employments or any combination of duties of any such offices or employments may be held by the same officer or employee at the same time. The offices or employments so merged and combined shall always be construed to be separate, and the effect of the combination or merger shall be limited to a consolidation of official duties only. The salary or compensation of the officer or employee holding the merged and combined offices or employments or offices and employments shall not be in excess of the maximum amount provided by law for the salary or compensation of the office, offices, employment, or employments so merged and combined.