Utility costs at one UISZ Power Corporation's factories are listed below:

Month --- Machine hours --- Utility Cost $

Feb - 4421 - 39,308

Mar - 4268 - 39,573

Apr - 4234 - 39,392

May - 4237 - 39,394

Jun - 4299 - 39,787

Jul - 4318 - 39,881

Aug - 4305 - 39,798

Sep - 4308 - 39,831

Oct - 4226 - 39,315

Management believes that utility cost is a mixed cost that depends on machine- hours.

Question: Define total and unit fixed and variable cost.

Question: Why the distinction between the two types of costs is important.