RATE(nper,pmt,pv,fv,type,guess)
For a complete description of the arguments nper, pmt, pv, fv, and
type, see PV.
Nper is the total number of payment periods in an annuity.
Pmt is the payment made each period and cannot change over the life
of the annuity. Typically, pmt includes principal and interest but no other
fees or taxes. If pmt is omitted, you must include the fv argument.
Pv is the present value - the total amount that a series of future
payments is worth now.
Fv is the future value, or a cash balance you want to attain after
the last payment is made. If fv is omitted, it is assumed to be 0 (the
future value of a loan, for example, is 0).
Type is the number 0 or 1 and indicates when payments are due.
