Sec. 8.09. RETIREMENT BENEFIT PAYABLE TO DROP PARTICIPANT. The retirement benefit payable under Article 5 or 6 of this Act to a person who participates in the DROP:

(1) may not be increased as a result of any increase in the formula used in computing service retirement benefits under Section 5.04 of this Act that occurs after the effective date of the member's election to participate in the DROP;

(2) may not be increased as a result of any increase in the member's compensation that occurs after the effective date of the member's election to participate in the DROP;

(3) shall be increased by any annual cost-of-living adjustments under Section 9.04 of this Act that occur between the effective date of the member's election to participate in the DROP and the effective date of the member's retirement;

(4) may not be increased for additional service credit after the effective date of the member's election to participate in the DROP; and

(5) is subject to the limitations prescribed by Section 9.03 of this Act.