18.1A Calculating Equivalent Units L.O. 2, 3 Superior Lighting, Inc., mass-produces reading lamps. Materials used in constructing the body of the lamp are added at the start of the process, while the materials used in wiring the lamps are added at the halfway point. All labor and overhead are added evenly throughout the manufacturing process. Superior uses process costing and had the following unit production information available for the months of June and July: June July Number of lamps in beginning work in process 890 1,000 Lamps transferred to finished goods 3,300 2,930 Number of lamps in ending work in process 1,000 900 In June, the lamps in beginning work in process were approximately 80 percent complete, while those in ending work in process were only 30 percent complete. In July, the units remaining in ending work in process were 60 percent complete. All lamps in ending work in process are finished during the next month. a. For the month of June, calculate the equivalent units of production for the three major cost categories