Boardman Company reported the following data for the month of January: Inventories: Raw materials Work in process Finished goods 1/1 $32,000 $18,000 $30,000 1/31 $31,000 $12,000 $35,000 Additional information: Sales revenue $210,000 Direct labour costs 40,000| Manufacturing overhead costs 70,000 Selling expenses 25,000 Administrative expenses 35,000 Boardman Company's total conversion cost for January was: O a b d $110,000. $130,000. $135,000. $170,000