When the weighted-average method of process costing is used, a department's equivalent units are computed by: A. subtracting the equivalent units in beginning inventory from the equivalent units in ending inventory. B. subtracting the equivalent units in beginning inventory from the equivalent units for work performed during the period. C. adding the units transferred out to the equivalent units in ending inventory. D. subtracting the equivalent units in beginning inventory from the sum of the units transferred out and the equivalent units in ending inventory.