Commencing October 1, 1998, there is provided to each person currently receiving benefits whose effective date of retirement was prior to October 1, 1998, for purposes of receiving benefits, and to certain beneficiaries of deceased members and deceased retirees currently receiving survivor benefits, if the effective date of retirement or death for the deceased retiree or deceased member was prior to October 1, 1998, for purposes of receiving benefits from the Teachers' Retirement System, a cost-of-living increase of not less than thirty dollars ($30) per month and the increase shall be more if determined as follows:
(1) Four percent of the current gross benefit paid to the retiree and to certain beneficiaries of deceased members and deceased retirees.
(2) Two dollars ($2) per month for each year of service attained by the retiree for each retiree selecting the maximum retirement allowance or option one.
(3) Two dollars ($2) per month for each year of service attained by the retiree reduced by the retiree's option election factor for each retiree selecting option two, three, or four unless the beneficiary under the option selected is deceased on July 1, 1998, in which case the increase shall not be reduced.
(4) Two dollars ($2) per month for each year of service attained by the deceased member or deceased retiree reduced by the survivor's option factor for each beneficiary receiving monthly benefits from the Teachers' Retirement System.