The mayor and associate commissioners shall continue to receive their respective salaries and allowances until the expiration of their respective terms of office. In addition, all reasonable expenses incurred by such mayor and associate commissioners in the performance of their duties as such mayor and associate commissioners shall be paid by the city. All such salaries shall be payable by the city in equal monthly installments and at the same rate for every fraction of a year which the commissioners serve. After the expiration of the term or terms of office of the present mayor and each associate member now holding office, the Mayor of Dothan shall receive an annual salary of fourteen thousand four hundred dollars ($14,400) and each associate commissioner shall receive an annual salary of seven thousand two hundred dollars ($7,200). All such salaries and expense allowances shall be payable by the city in equal biweekly installments and at the same rate for every fraction of a year which the commissioners serve. The payment of all funds out of the treasury shall be by warrants signed by the city clerk and countersigned by the mayor, provided that during the absence of the mayor from the corporate limits of the city, and necessity therefor arising, warrants may be countersigned by one of the associate commissioners designated by the mayor to act in his or her stead. All such disbursements shall be authorized by resolution of the commission or by voucher signed by the city clerk-treasurer and three members of the commission.