Perpetual inventory using FIFO

Beginning inventory, purchases, and sales for Item Zeta$9$ are as follows:

Oct. $1$ Inventory

Oct. $7$ Sale

Oct. $15$ Purchase

Oct. $24$ Sale

Assuming a perpetual inventory system and using the first$-$in$,$ first$-$out $($FIFO$)$ method, determine $($a$)$ the cost of goods sold on

October $24$ and $($b$)$ the inventory on October $31.$

a$.$ Cost of goods sold on October $24$

b$.$ Inventory on October $31$

a$.$ When the FIFO method is used, costs are included in cost of goods sold in the order in which they were purchased.

Think of your inventory in terms of "layers". Determine how much inventory remains from each layer after each sale.

b$.$ The ending inventory is made up of the most recent purchases.