Express Distribution markets CDs of the performing artist Fishe. At the beginning of October, Express had in beginning inventory 2,000 of Fishes CDs with a unit cost of $7. During October, Express made the following purchases of Fishes CDs.

Oct. 3 2,500 @ $8

Oct. 19 3,000 @ $10

Oct. 9 3,500 @ $9

Oct. 25 4,000 @ $11

During October, 10,900 units were sold. Express uses a periodic inventory system.

I can not figure out how to get LIFO (Ending Inventory and Cost of Goods Sold)