B. For a member whose membership in ASRS commenced before July 1, 2011, the benefit payable to a member electing early retirement shall be determined by reducing the normal retirement benefit computed in accordance with section 38-757 either:

1. 1. At the rate of three percent per year from age sixty to age sixty-five and five percent per year from age fifty to age sixty. The reduction in normal retirement benefits pursuant to this paragraph for an eligible member electing early retirement shall be based on the period from the date of commencement of early retirement benefits to the member's sixtieth birthday if the member has at least twenty years of total credited service, sixty-second birthday if the member has at least ten but less than twenty years of total credited service or sixty-fifth birthday if the member has at least five but less than ten years of total credited service.
2. 2. If the sum of a member's age and years of total credited service equals seventy-seven or more, but is less than eighty, at the rate of three percent for each unit of one or fraction of one by which the sum is less than eighty.