Staffer Corp uses a predetermined overhead rate based on direct labor hours to apply manufacturing overhead. Manufacturing overhead cost and direct labor hours were estimated at $117,800 and 19,000 hours, respectively, for the year. The companys labor rate is $18 per hour. By the end of the year, Staffer had incurred $331,200 in total labor costs and $122,750 in actual manufacturing overhead cost. Manufacturing overhead for the year was: a. $8,670 under-applied b. $8,670 over-applied c. $4,950 under-applied d. $4,950 over-applied e. $3,720 under-applied f. $3,720 over-applied g. $10,800 under-applied h. $10,800 over-applied