To know whether the returns are large enough to produce a profit or surplus, we need a way to compare money returns in the future with money outflows (i.e. investment now).
Kujua kama anarudi ni kubwa ya kutosha kuzalisha faida au ziada, tunahitaji njia ya kulinganisha fedha anarudi katika siku zijazo na outflows fedha (k.v. uwekezaji sasa).