(a) Effective January 1, 1976, any pension being paid under this chapter to an individual 60 years of age or older shall be increased by either:
(b) Any pension under this chapter that is payable on February 15, 1980, shall be increased effective January 1, 1979, by $20 per month.
(c) Any pension under this chapter that is payable on April 24, 1984, shall be increased effective July 1, 1984, by $30 per month.
(d) Any pension under this chapter that is payable on the date this subsection is enacted into law shall be increased effective July 1, 1986, by $30 a month.
(e) Any pension under this chapter that is payable on July 13, 1988, shall be increased effective July 1, 1988, by $105 a month.
(f) Any pension under this chapter that is payable on the date this subsection is enacted into law shall be increased effective July 1, 1990, by $60 a month.