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Inventory
3 Months Ended
Sep. 30, 2011
INVENTORY

2. INVENTORY

The following table summarizes the Company's inventory balances as of September 30, 2011 and December 31, 2010:

  September 30, December 31,
  2011 2010
       
  (in millions)
Coal, fuel oil and other raw materials $ 377 $ 276
Spare parts and supplies   291   285
Total $ 668 $ 561