The Three Identical Units of Product Basic H Are Purchased

The three identical units of Product Basic H are purchased during July, as shown below.
$$\begin{array} { | l | l | l | l | } \hline \text { Date } & \text { Product Basic H } & \text { Cost } \\\hline \text { July } 3 & \text { Purchase } & 1 & \$ 35 \\\hline \text { July } 10 & \text { Purchase } & 1 & \$ 36 \\\hline \text { July } 24 & \text { Purchase } & 1 & \$ 37 \\\hline & \text { Total } & 3 & \$ 108 \\\hline & & & \\\hline & \text { Average cost per unit } & \$ 36 & \\\hline\end{array}$$ Assume one unit sells on July 28 for $45.
Determine the gross profit, cost of merchandise sold, and ending inventory on July 31 using (a) first in first out, (b) last in last out, (c) average cost flow methods.