The plant manager's forecast would be

$1443$

too high if he$/$she uses the

$$

to predict costs.

The

$$

is based on a mixed cost that will change as volume changes. If the manager uses this

method, he$/$she is erroneously assuming that the

$$

does not change at different volumes. The

manager should use the

$$

to predict costs since it correctly takes into account the variable and

fixed components of producing mailboxes.