Use the last$-$in$,$ first$-$out $($LIFO$)$ cost allocation method, with perpetual inventory updating, to calculate $($a$)$ sales revenue, $($b$)$ cost of goods sold, and c$)$ gross margin for A$75$ Company, considering the following transactions.

Number of Units Unit Cost

Beginning Inventory $105$  $$40$

Purchased Mar. $2150$  $$42$

Sold Mar. $31$ for $$75$ per unit $88$