(b) A member who had been contributing for service retirement benefits on the basis of any of the plans contained in subparagraph a hereof, shall receive at retirement, for service rendered before April first, nineteen hundred sixty, a pension computed on the basis of one-one hundred twentieth of his final average salary for each year of credited member service plus one-sixtieth of his final average salary for each such year of credited prior service or service in war after world war I. Notwithstanding anything to the contrary contained in section seventy-five of this chapter, a member who had been contributing as aforesaid shall be eligible for superannuation retirement upon attainment of age fifty-five. 2. A member who had been contributing for service retirement benefits on the basis of the plan contained in section eighty of this chapter shall receive at retirement, for service rendered on or after April first, nineteen hundred sixty, a pension of one-fortieth of his final average salary for each year of such credited service, provided, however, that the sum total of the retirement allowance payable shall not exceed one-half of the member's final average salary. 3. A member who had been contributing under section eighty-nine shall receive at retirement, for service rendered on and after April first, nineteen hundred sixty, a pension of one-fiftieth of his final average salary for each year of such credited service, with the total allowance hereunder determined as defined and limited in the section referred to in this paragraph three and with the additional proviso that any contributions made by the member during the period referred to in this paragraph three are to be used at retirement to provide an additional annuity over and above the retirement allowance otherwise provided, except that persons who last became members on or after July first, nineteen hundred seventy-three, shall receive such pension only for service rendered on and after April first, nineteen hundred sixty, and prior to July first, nineteen hundred seventy-four. 4. A member who had been contributing under section eighty-nine-a shall receive at retirement, for service rendered on and after April first, nineteen hundred sixty, a pension of one-fiftieth of his final average salary for each year of such credited service, with the total allowance hereunder determined as defined and limited in the section referred to in this paragraph four and with the additional proviso that any contributions made by the member during the period referred to in this paragraph four are to be used at retirement to provide an additional annuity over and above the retirement allowance otherwise provided; except that persons who last became members on or after July first, nineteen hundred seventy-three shall receive such pension only for service rendered on and after April first, nineteen hundred sixty and prior to July first, nineteen hundred seventy-four. 5. In addition to the pension hereinabove provided, a member shall receive an annuity which shall be the actuarial equivalent of his accumulated contributions at the time of his retirement. 6. The benefits hereinabove provided shall be payable unless the member would otherwise under the provisions of this chapter be entitled to a greater benefit, in which event, the greater benefit shall be payable. 7. An act of the legislature of the year nineteen hundred sixty-eight which in form, adds or purports to add a new section or subdivision or purports to amend or repeal any section, subdivision or provision of this chapter as in force and effect immediately prior to January first, nineteen hundred sixty-eight, shall be deemed and construed as having been added to this act and shall be given full effect according to its context as if the same had been added expressly and in terms of this act, and shall be deemed and construed to have been inserted in this act in the appropriate position in regard to and as modifying the effect of the corresponding provision or provisions of this act to the end that there will be no diminution or impairment of any of the benefits enacted by such session of the legislature.