Perpetual Inventory Using LIFO

Beginning inventory, purchases, and sales for Item CZ$83$ are as follows:

$\backslash$table$[[$January $1,$Inventory,$84$ units @ $$30.$ January $5,$ Sale, $67$ units. January $11,$ Purchase, $93$ units @ $$33.$ January $21,$ Sale, $78$ units. Assuming a perpetual inventory system and using the last$-$in$,$ first$-$out $($LIFO$)$ method, determine $($a$)$ the cost of merchandise sold on January $21$ and $($b$)$ the inventory on January $31.$