For one contract period, we sum all all in-going cash flows of
an actor over the contract period and subtract the sum of all
out-going cash flows, including investments. If we do this for all
periods in a time series, the net present cash flow of a time series
is

where p ranges over the periods of the time series.

For example, consider table 7.1. In period 0, an investment is made
and no revenues and expenses occur yet. In periods 1, 2 and 3 we
have a revenues of f500 and expenses of f100 in each period.
This gives a positive net cash flow of f200 at the end of the time
series.

Table 7.1:Naive calculation of net cash value over a series of market
scenarios.