Answer:
Flounder Corp.
                                    Weighted Average      FIFO             LIFO
Ending Inventory              $1,414                   $1,580           $1,280
Cost of goods sold          $2,796                 $2,630          $2,930
Explanation:
a) Data and Calculations:
Date        Explanation      Units     Unit Cost     Total Cost
June 1     Inventory            100          $5               $ 500 
June 12   Purchases         385            6                 2,310     
June 23  Purchases        200             7                 1,400
                Total units        685                            $ 4,210
June 30  Inventory          230
June 30  Units Sold        455  (685 - 230)
Weighted Average Cost = Total costs/Total units bought
= $4,210/685 = $6.146
Weighted Average:
Ending Inventory = $1,414 ($6.146 * 230)
Cost of goods sold = $2,796 ($6.146 * 455)
FIFO:
Ending Inventory  = (30 * $6) + (200 * $7) = $1,580
Cost of goods sold = (100 * $5) + (355 * $6) = $2,630
LIFO:
Ending Inventory = (100 * $5) + (130 * $6) = $1,280
Cost of goods sold = (200 * $7) + (255 * $6) = $2,930
The weighted average method is based on an average cost for estimating the cost of ending inventory and cost of goods sold.  The FIFO method assumes that goods bought initially are the first to be sold while the LIFO method assumes that goods bought last are the first to be sold.