How do you calculate unadjusted rate of return with depreciation?

To calculate unadjusted rate of return with depreciation:

Subtract depreciation cost from the expected cash flows along with expenses, then multiply the result by the income tax rate and subtract. Calculate average investment 10,000/2

Example: Machine Investment $10,000 4 year life , Expected cash flows 8,000 expenses 2,200 tax rate 20%

(8,000-2,500-2.200) x (1 -.20) = 2,640/5,000 = 52.80%