A manufacturing company applies factory overhead based on direct labor hours. At the beginning of the year, it estimated that factory overhead costs would be $331,581 and direct labor hours would be 49,349. Actual manufacturing overhead costs incurred were $322,791, and actual direct labor hours were 51,159. What is the predetermined overhead rate per direct labor hour?

a. $6.31 b. $6.54 c. $6.72 d. $ 6.48