Which increment should be examined first in incremental rate of return analysis, if MARR = 12.0%?

check here (https://www.chegg.com/homework-help/questions-and-answers/increment-examined-first-incremental-rate-return-analysis-marr-120-c-c-b-b-q22575259) for a reference. please explain how incremental inflow is found.

Do-nothing A D C $6,000 $3,000 $6,500 $3,000 |First cost 1,370 1,128 644 509 Annual benefit Life 10 yrs ROR 13.5% 16.5% 11.0% 17.0% C-A A-C - - Do-nothing A D C $6,000 $3,000 $6,500 $3,000 |First cost 1,370 1,128 644 509 Annual benefit Life 10 yrs ROR 13.5% 16.5% 11.0% 17.0% C-A A-C - -