How the payback= 4.31 was calculated?

TABLE 10.11 Projected Total Cash flows Year 0 5 6 Capital spending $(800.000) Operating cash flow Change in NWC Total project cash flow $(820.000) $105,600 $136,300 $215,500 $255,100 $232,000 $215,500 $182,500 $149,500 116,500 20,000) (34,000) (36,000) (18,000) 750 8,250 16.500 16.500 66,00 Total project cash fow $1820,000 102.300 $179.500 237,100 $232,750 $223,750 $199,000 $166,000 $28810 $179,500 $237,100 $232.750$23,750 $199,000 flow $(820,000) $717,700) $(538.200) $(301,100) $ (68.350) $155,400 $354,400 $520,400 $520,400 $808,50 Discounted cash flow(820 88,957 135,728 15,897 133,076 111,243 86,033 62,406 94, ,000) t present value $47,519 IRR 4.31 years