Custom Company has two manufacturing departments - Fabrication and Finishing. The predetermined overhead rates in Fabrication and Finishing are $19.00 per direct labour hour and 120% of direct materials cost, respectively. The direct labour wage rate is $17.00 per hour in Fabrication. The following information is on Job 800: Fabrication Finishing Direct materials $420 $70 Direct labour $153 $57 Required: a. What is the total manufacturing cost assigned to Job 800? (2 marks) b. Why do companies use predetermined overhead rates rather than actual manufacturing costs to apply overhead to jobs?