Section 15.  Salary.
   (a)   Salary of Mayor – The Mayor shall be compensated at a rate as set from time to time by an ordinance passed by the council in the regular course of business. Provided, however, that no change shall be made in the salary for any mayor during the term for which he was elected. The ordinance making any change in the salary paid to the mayor, either by way of increase of [or] decrease, shall be finally ordained prior to the municipal election to elect the next succeeding mayor, and shall take effect only as to the next succeeding mayor.
   (b)   Salary of councilmembers – Each councilmember shall receive an annual salary the amount of which shall be specified from time to time by an ordinance passed by the council in the regular course of its business. The salary for each councilmember shall be equal except that the salary specified at the time any councilmember takes office shall not be changed during the period for which the councilmember was elected.