Kingsport Containers Company makes a single product that is subject to wide seasonal variations in demand. The company uses a job-order costing system and computes plantwide 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: Direct materials Direct labor Manufacturing overhead Total manufacturing costs (a) Number of units to be produced (b) Estimated unit product cost (a) (b). Quarter First $ 200,000 Second $ 100,000 60,000 206,000 $ 366,000 60,000 $ 6.10 Third $ 50,000 Fourth $ 150,000 30,000 194,000 $ 274,000 90,000 ? $ ? 30,000 $ 9.13 90,000 $ ? 120,000 230,000 $ 550,000 120,000 $ 4.58 Management finds the variation in quarterly unit product costs to be confusing. It has been suggested that the problem lies with manufacturing overhead because it is the largest element of total manufacturing cost. Accordingly, you have been asked to find a more appropriate way of assigning manufacturing overhead cost to units of product.