Opus uses the convention in which cash inflows are
represented by positive numbers, while cash outflows are
represented by negative numbers.

Type = 1 means ordinary annuity.
Type = 0 means annuity due.
Number of periods (NPER) is synonymous with "term."

All arguments are required.

PV(rate,nper,pmt,fv,type) computes present value.
FV(rate,nper,pmt,pv,type) computes future value.
PMT(rate,nper,pv,fv,type) computes payment.
NPER(rate,pmt,pv,fv,type) compute number of periods.
RATE(nper,pmt,pv,fv,type,guess) computes interest rate.
