JB Adams Inc. had the following purchase transactions in May Number of Units Total Cost Cost per Unit $4 500 Date of Purchase May 5 May 10 May 15 700 $6 $2,000 $4,200 1,800 400 $4.50 Adams sells 1,200 units on May 20 and uses the LIFO method of inventory costing. What is Adams' Cost of Goods Sold? 6,000 6,200 6,400