Sanger Inc. manufactures high-quality clocks. For the month ending September 30, 2021, Sanger began 10,000 units and completed 8,000 units. This left 2,000 units in process 50% complete. For this period, what were the number of equivalent units of production that Sanger had? O a. 18,000 O b. 1,000 Oc. 9,000 O d. 8,000 To calculate equivalent units, companies: O a. Must use the weighted average cost method O b. Must use the FIFO method. O c. Must use the LIFO method. O d. Can choose between the weighted average cost and FIFO methods