Function            PV - calculate the Present Value of a single
                             amount

  Syntax              double PV(double payment, double interest, int
                                periods)

  Prototype in        finance.h

  Remarks             PV calculates the Present Value of a single amount
                      given the future value of the principal, the
                      interest rate per period and the number of periods.

  Return value        returns the present value of a single amount.

  See also            FV(), FVa(), PMT(), PVa()