The following cost functions were developed for manufacturing overhead costs: Manufacturing Overhead Cost Cost Function Electricity $200 + $20 per direct labor hour Maintenance $400 + $30 per direct labor hour Supervisors' salaries $20,000 per month Indirect materials $16 per direct labor hour

If June production is expected to be 2,000 units requiring 3,000 direct labor hours, what is the estimated manufacturing overhead costs? Also discuss the role of direct labor hours in determining the predetermined overhead rates.