Would I be able to get some assistance on how the formula should be written with an explanation?

Determine the discounted payback period using after-tax cash flows. (Round present value factor calculations to 5 decimal places, e.g. 1.25124 and final answer to 2 decimal places e.g. 5,125.36.) Discounted payback period Find the ARR. (Round answer to 1 decimal place, e.g. 15.2\%.) ARR % Calculate the profitability index for this investment. (Round answer to 2 decimal places, e.g. 15.25.) Profitability index