Javadi Company makes a single product that is subject to wide seasonal variations in demand. The company uses a job-order costing system and computes predetermined overhead rates on a quarterly basis using the number of units to be produced as the allocation base. Its estimated costs, by quarter, for the coming year are given below: Quarter First Second Third Fourth Direct materials $ 160,000 $ 80,000 $ 40,000 $ 120,000 Direct labor 80,000 40,000 20,000 60,000 Manufacturing overhead 240,000 216,000 204,000 ? Total manufacturing costs (a) 480,000 $ 336,000 264,000 $ ? Number of units to be produced (b) 160,000 80,000 40,000 120,000 Estimated unit product cost (a