Assume that at the beginning of the year a firm estimates its overhead costs at $100,000. The firm plans to use job order costing and will use direct labor hours as its base. Direct labor hours for the year were estimated at 50,000. At the end of the year, the firm incurred 51,000 actual direct labor hours and the actual overhead cost was $112,000. Which of the following best describes why overhead was under-allocated in this case?