Gnarly Company uses a job-order costing system. The company applies manufacturing overhead to jobs using a predetermined overhead rate based on direct labor-hours. Last year, manufacturing overhead and direct labor-hours were estimated at $80,000 and 16,000 hours respectively, for the year. In June, Job #315 was completed. Materials costs on the job totaled $1,500 and labor costs totaled $2,400 at $6 per hour. At the end of the year, it was determined that the company worked 15,000 direct labor-hours for the year, and incurred $78,000 in actual manufacturing overhead costs. Required: (show explanations/work on calculations!) a. Determine the predetermined overhead rate for the year. b. Determine the amount of overhead charged to jobs during the year. c. Determine the amount of underapplied or overapplied overhead for the year. d. Assuming that 100 units were completed, determine the unit cost that would appear on the job cost sheet for Job #315.