At the beginning of 2011, the Gilbert Companys work in process inventory account had a balance of $30,000. During 2011, $68,000 of direct materials were used in production, and $66,000 of direct labor costs were incurred. Factory overhead in 2011 amounted to $90,000. Cost of goods manufactured is $220,000 in 2011. The balance in work in process inventory on December 31, 2011, is: a. $34,000 b. $24,000 c. $66,000 d. $6,000