An accounting firm, Shultz & Worsk, accumulates costs associated with individual cases using a job order cost system. For the upcoming year, the firm estimates that it will use 30,000 hours of direct labor for professional staff at an hourly rate of $150 per hour. Estimated total overhead costs are $900,000. The firm allocates overhead costs to individual client services on the basis of direct labor hours of its professional staff. What is the firm's predetermined overhead rate for the upcoming year?