NPV (Net Present Value)

[ See also Net Present Value @ Wikipedia ]

where

$//<![CDATA[ \begin{array}{l}t\end{array} //]]>$ – time passed since the first investment,

$//<![CDATA[ \begin{array}{l}r = \rm \frac{Cash_{out} - Cash_{in}}{Cash_{in}}\end{array} //]]>$ – the discount rate, i.e. the return that could be earned per unit of time on an investment with similar risk

$//<![CDATA[ \begin{array}{l}n\end{array} //]]>$ – total number of time steps

$//<![CDATA[ \begin{array}{l}R_t = \rm Cash_{in}(t) - \rm Cash_{out}(t)\end{array} //]]>$ – the net cash flow at time step t. 

$//<![CDATA[ \begin{array}{l}R_0 = - \rm Cash_{out}(t=0)\end{array} //]]>$ – the initial investment at time step t = 0.