Savanah Manufacturing uses a weighted-average process costing system. All materials at Savanah are added at the beginning of the production process. The equivalent units for materials at Savanah would be the sum of: Savanah Manufacturing uses a weighted-average process costing system. All materials at Savanah are added at the beginning of the production process. The equivalent units for materials at Savanah would be the sum of: units in beginning work in process and the units started. units in ending work in process and the units started. units in ending work in process and the units started and completed. units in beginning work in process and the units started and completed