(a) On or after October 1, 1969, there is hereby provided to any teacher who was receiving a retirement allowance from the Teachers' Retirement System of Alabama and who was retired prior to October 1, 1969, an increase in his or her maximum retirement allowance in the amount of 10 percent, excluding those whose monthly retirement allowance is as much as $400.00 and that such increase shall be limited so as to provide not to exceed a maximum retirement allowance of $400.00 per month.
(b) The Board of Control of the Teachers' Retirement System shall administer all the benefits provided by this section under such rules and regulations as the said Board of Control may adopt not inconsistent herewith.
(c) The Board of Control of the Teachers' Retirement System shall determine annually the amount required to pay the cost of the benefits provided in this section and shall notify the chief fiscal officer of each employer the percentum rate of earnable compensation of the members required to be paid the retirement system. Each employer of members of the Teachers' Retirement System of Alabama shall pay on account of the increases provided in this section in the same manner and from the same source of funds as is provided in Section 16-25-21, it being the intent of the Legislature that the costs of providing the increases provided in this section shall be distributed from all funds in proportion to the salaries paid therefrom for active members.