Johnson Company had 500 units of "Tank" in its inventory at a cost of $4 each. It purchased, for $2, 800, 300 more units of "Tank". Johnson then sold 400 units at a selling price of $10 each, resulting in a gross profit of $1, 600. The cost flow assumption used by Johnson is FIFO. is LIFO. is weighted average. cannot be determined from the information given