Three identical units of merchandise were purchased during July, as follows: Date Product T Units Cost July 3 Purchase 1 $17.00 10 Purchase 1 20.00 24 Purchase 1 23.00 Total 3 $60.00 Average cost per unit $20.00 Assume one unit sells on July 28 for $30.00. Determine the gross profit, cost of goods sold, and ending inventory on July 31 using (a) first-in, first-out, (b) last-in, first-out, and (c) average cost flow methods.