Cosby uses a weighted-average process-costing system. All materials are added at the beginning of the process; conversion costs are incurred evenly throughout production.The company finished 40,000 units during the period and had 15,000 units in progress at year-end, the latter at the 40% stage of completion.Total material costs amounted to $220,000; conversion costs were $414,000.The cost of goods completed is: $312,000. $414,000. $520,000. $634,000. some other amount.