NPV (Net Present Value)

[ See also Net Present Value @ Wikipedia ]

where

$//<![CDATA[ \begin{array}{l}t_i\end{array} //]]>$ – time passed since the first investment ( assuming that  $//<![CDATA[ \begin{array}{l}t_0 = 0\end{array} //]]>$),

$//<![CDATA[ \begin{array}{l}r = \rm \frac{Cash_{out} - Cash_{in}}{Cash_{in}}\end{array} //]]>$ – 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

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

$//<![CDATA[ \begin{array}{l}R_0 = - \rm Cash_{out}(t=0)\end{array} //]]>$ – the volume of cash investment at initial time moment  $//<![CDATA[ \begin{array}{l}t_0 = 0\end{array} //]]>$.