Fill in the Missing Data for Company C

Fill in the missing data for Company C:
$\begin{array}{|l|c|}\hline & \text { Company C } \\\hline \text { Direct materials used } & \$ 6,000 \\\hline \text { Direct labor cost } & \text { (a) } \\\hline \text { Overhead } &7 , 000 \\\hline \text { Total manufacturing costs } & 18,000 \\\hline \text { Work in process inventory, Jan. } 1 & 2,000 \\\hline \text { Work in process inventory, Dec. } 31 & \text { (b) } \\\hline \text { Sales revenue } & 30,000 \\\hline \text { Finished goods inventory, Jan. } 1 & 7,000 \\\hline \text { Cost of goods manufactured } & \text { (c) } \\\hline \text { Cost of goods available for sale } & 23,000 \\\hline \text { Finished goods inventory, Dec. } 31 & \text { (d) } \\ \hline \text { Cost of goods sold } & 18,000 \\\hline \text { Gross margin } & \text { (e) } \\\hline \text { Operating expenses } & \text { (f) } \\\hline \text { Operating income } & 3,000\\\hline\end{array}$