Express Distribution markets CDs of the performing artist Fishe. At the beginning of October, Express had in beginning inventory 4,300 of Fishe's CDs with a unit cost of $6. During October, Express made the following purchases of Fishe's CDs Oct. 3 5,375@ $7 Oct. 19 6,450@ $9 Oct. 9 7,525@ $8 Oct. 25 8,600@ $10 During October, 23,435 units were sold. Express uses a periodic inventory system