Vulcan Co. uses the perpetual inventory method. The inventory records for Vulcan reflected the following: Jan 1 Beginning Inventory 300 units @ $2.10 Jan 12 First Purchase 400 units @ $2.40 Jan 18 Sales 500 units @ $3.00 Jan 21 Second Purchase 300 units @ $2.20 Jan 25 Third Purchase 100 units @ $2.30 Jan 31 Sales 400 units @ $3.00 Assuming Vulcan uses a FIFO cost flow method, the cost of goods sold for the sales transaction on January 31 is: a. $880. b. $840. c. $920 d. $860