State the purpose for each of the following built-in spreadsheet functions.
(a) PV (1%,n,A,F)
(b) FV (1%,n,A,P)
(c) RATE (n.A.P.F)
(d) IRR(first_cell:last_cell)
(e) PMT(1%.n.P.F)
(f) NPER(1%,A,P.F)