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Inventory
3 Months Ended
Jun. 30, 2012
INVENTORY

2. INVENTORY

The following table summarizes the Company's inventory balances as of June 30, 2012 and December 31, 2011:

  June 30, December 31,
  2012 2011
       
  (in millions)
Coal, fuel oil and other raw materials $ 452 $ 444
Spare parts and supplies   374   341
Total $ 826 $ 785