Three identical units of merchandise were purchased during July, as follows: Date Product Basic H Units Cost July 3 Purchase 1 $35 10 Purchase 1 36 24 Purchase 1 37 Total 3 $108 Average cost per unit $36 Assume one unit sells on July 28 for $45. Determine the gross profit, cost of merchandise sold, and ending inventory on July 31 using the (a) first-in, first-out, (b) last-in, first-out, and (c) average cost flow methods.