PV  - script and chart function
                This function returns the present value of an investment.
PV(rate, nper, pmt [ ,fv [ , type ] ])
Return data type: numeric. By default, the result will be formatted as currency..
The present value is the total amount that a series of future payments is worth right now. For example, when borrowing money, the loan amount is the present value to the lender.
Arguments:
| Argument | Description | 
|---|---|
| rate | The interest rate per period. | 
| nper | The total number of payment periods in an annuity. | 
| 
                                 pmt  | 
                            The payment made each period. It cannot change over the life of the annuity. A payment is stated as a negative number, for example, -20. | 
| 
                                 fv  | 
                            The future value, or cash balance, you want to attain after the last payment is made. If fv is omitted, it is assumed to be 0. | 
| 
                                 type  | 
                            Should be 0 if payments are due at the end of the period and 1 if payments are due at the beginning of the period. If type is omitted, it is assumed to be 0. |