Perpetual inventory using LIFO

Beginning inventory, purchases, and sales for Item $88-Hx$ are as follows:

Assuming a perpetual inventory system and using the last$-$in$,$ first$-$out $($LIFO$)$ method, determine $($a$)$ the cost of goods sold on July $27$ and $($b$)$ the inventory on July $31.$

a$.$ Cost of goods sold on July $27$

b$.$ Inventory on July $31$