18-35 WEIGHTED-AVERAGE METHOD, SPOILAGE. Rounder specializes in the manufacture of ball bearings for aircraft. Direct materials are added at the start of the production process. Conversion costs are added evenly during the process. Some units of this product are spoiled as a result of defects not detectable before inspection of finished goods. Normally, the spoiled units are 15% of the good units transferred out. Spoiled units are disposed of at zero net disposal price. LO 2 1. Normally spoiled units, 210 Rounder uses the weighted-average method of process costing. Summary data for September 2018 are