Bolka Corporation, a merchandising company, reported the following results for October: Sales $ 413,000 Cost of goods sold (all variable) $ 169,100 Total variable selling expense $ 20,700 Total fixed selling expense $ 17,900 Total variable administrative expense $ 13,100 Total fixed administrative expense $ 30,400 The gross margin for October is:a. $210,100 b. $364,700 c. $161,800 d. $243,900