At the beginning of the year, Monroe Company estimates annual overhead costs to be $600,000, and that 300,000 machine hours will be operated. Using machine hours as a base. Company used 315,000 machine hours in producing their jobs. Moreover, the actual manufacturing overhead incurred during a year $650,000. The amount of under or over-applied overhead is: a. $20,000 under-applied. b. $50,000 over-applied. c. $30,000 under-applied. d. $20,000 over-applied.