Metlock, Inc. just began business and made the following four inventory purchases in June: June 1 June 10 June 15 June 28 135 units 180 units 180 units 135 units $940 1400 1510 1190 $5040 A physical count of merchandise inventory (rounded to whole dollar) on June 30 reveals that there are 190 units on hand. The inventory method which results in the highest gross profit for June is not determinable. the FIFO method. the LIFO method. the average cost method