Perpetual Inventory Using FIFO

Beginning inventory, purchases, and sales for Item ER$27$ are as follows:

$\backslash$table$[[$May $1,$Inventory,$77$ units @ $$21],[9,$Sale,$60$ units$],[13,$Purchase,$67$ units @ $$24],[25,$Sale,$21$ units$]]$

Assuming a perpetual inventory system and using the first$-$in$,$ first$-$out $($FIFO$)$ method, determine $($a$)$ the cost of merchandise sold on May $25$ and $($b$)$ the inventory on May $31.$

a$.$ Cost of merchandise sold on May $25$$

b$.$ Inventory on May $31$