After determining the expected cash flows and appropriate interest rate, the last step in the valuation process is to find the total PV of all cash flows. The PV of the cash flow depends on the timing of the cash flow, i.e., when we receive the cash flow, and on the interest rated which is used as the discount factor.
Assume, The PV of an expected cash flow to be received n years form now if a discount rate r can be earned on any sum invested today is:
PV_{n} = ...Eq.(1)
Then the value of the financial instrument is the sum of the PV of all the expected cash flows. Assume that there are M expected cash flows:
Value of financial instrument = PV_{1 }+ PV_{2 }+ PV_{3}...PV_{M } ...Eq.(2)