What kind of firm would use a job order cost system?

A job order cost system is one in which a firm counts the
costs for each separate "batch" of work separately.  In other words, the company treats
different jobs as separate things and therefore tracks the costs of each job separately
from the other jobs.  Because of this, a firm that uses this sort of system should be
one whose jobs are not all the same.

For example, a car
company that makes the same kind of car all day every day should not use this system. 
All its jobs are the same and so this system would not be appropriate.  However, if a
firm did many kinds of custom jobs (say, for example, publishing all sorts of different
text books), it would be much more appropriate to use the job order cost
system.

In short, then, the kind of firm that should use
this system is a firm that does many jobs that are distinguishable from one
another.