Assigning Costs to Products: Weighted Average Method. Sydney, Inc., uses the weighted average method for its process costing system. The Assembly department at Sydney, Inc., began April with 6,000 units in work-in-process inventory, all of which were completed and transferred out during April. An additional 8,000 units were started during the month, 3,000 of which were completed and transferred out during April. A total of 5,000 units remained in work in-process inventory at the end of April and were at varying levels of completion, as shown in the following. Direct materials 40 percent complete Direct labor 30 percent complete Overhead 50 percent complete