$"10.$ Kelso Manufacturing allocates manufacturing overhead using a single predetermined rate based on a planned use of $15,000$ direct labour hours per year. Company leadership recently learned that its costing system may be too simple for its operations, and that job costs may be fairly inaccurate. A consultant was hired to study overhead costs, and the following information reflects the cost pools and activity rates that were determined:

$"$

Job #$156$ required $25$ purchase orders, $400$ direct labour hours, $50$ production runs, and $100$ inspections. If a traditional costing system was used, this job would be:

a$.$

Overcosted by $$6,400$

b$.$

Overcosted by $$12,000$

c$.$

Overcosted by $$5,600$

d$.$

Undercosted by $$3,500$