(a) All former governors of the State of Alabama upon reaching the age of 60 shall be entitled to a monthly retirement payment out of the General Fund in the State Treasury which shall equal 68 percent of the Governor's salary if said former governor had served for one full term or less; the amount paid shall equal 100 percent of the Governor's salary if he has served two full terms or more.

(b) All former governors of the State of Alabama, regardless of age, who sustain permanent total physical or mental disability during their terms of office, by accident or otherwise, shall be entitled to their full salary for life upon leaving office.

(c) Said payments shall be paid out of the General Fund in the State Treasury on a monthly basis each and every month once a former governor becomes eligible for such payments. A former governor eligible for compensation under subsection (b) of this section shall not receive payment under subsection (a) of this section.

(d) Disability under subsection (b) of this section shall be determined as of the date the person so entitled leaves the Governor's office by resignation or otherwise. Proof shall be made by any interested party to the state Finance Director, who shall promptly certify the fact of disability to the state Comptroller. It shall be considered sufficient proof if three practicing physicians certify under oath that a former governor is so permanently totally disabled.

(e) Any law or part of law to the contrary notwithstanding, the state Comptroller shall cause to be deducted from the salary paid to a Governor of the State of Alabama, being subject to this section, which provides for payment of retirement benefits to former governors, 10 percent of his earnable compensation; such deduction to be deposited by the Comptroller in the General Fund in the State Treasury.