The present value formula is applied to each of the cashflows from year zero to year five. For example, the cashflow of -$250,000 in the first year leads to same present value during the year zero, while the inflow of $100,000 during the second year (year 1) leads to present value of $90,909. Generally, NPV can be calculated with the formula NPV = ⨊(P/ (1+i)t) – C, where P = Net Period Cash Flow, i = Discount Rate (or rate of return), t = Number of time periods and C = Initial Investment. For an internal company calculation, you should use a discount rate in NPV, not an interest rate. The discount rate is the rate of return you could get from an investment with a similar risk profile in the financial markets — for your company. This is going to vary from company to company…your brother’s chimney