Materials inventory, December 1 $56,220 $73,090 82,590 Materials inventory, December 31 Materials purchased 142,800 (a) Cost of direct materials used in production 150,670 (b) Direct labor 211,950 164,450 Factory overhead 65,780 81,860 Total manufacturing costs incurred in December (b) 472,890 Total manufacturing costs 536,340 536,340 Work in process inventory, December 1 107,940 176,150 Work in process inventory, December 31 91,080 (c) Cost of goods manufactured (c) 468,510