\mbox{NPV} =  - \mbox{I}_0 + \mbox{DCF}  =  - \mbox{I}_0 + \sum_{i=1}^n \frac{\mbox{FCF}_i}{(1+r)^i} = \sum_{i=0}^n \frac{\mbox{FCF}_i}{(1+r)^i}

\mbox{FCF}_i = REV - OPEX