how can i calculate NPV and OFC?

sorry ocf

1 2 3 0 520,000 $ NPV System A Year Cost of System Annual Operating Costs Depreciation (520k/4years Total Expenses Before Tax Tax @25% Total Expenses After Tax Add back Depreciation Net Operating Cash Flow Total Cash Flow Discount Factor Discounted Cash Flows Net Present Value 145,000 145,000 145,000 145,000 130,000 $130,000 $130,000 $130,000 275,000 $275,000 $275,000 $275,000 68,750 $ 68,750 $ 68,750 $ 68,750 206,250 $206,250 $206,250 $206,250 130,000 $130,000 $130,000 $130,000 76,250 $ 76,250 $ 76,250 $ 76,250 76,250 $ 76,250 $ 76,250 $ 76,250 0.900900901 0.8116224 0.7311914 0.658731 68693.69369 61886 211 55753.343 50228 237 520,000 $ 1 520000 System A OCF NPV System B OCF NPV