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Inventory
3 Months Ended
Mar. 31, 2013
INVENTORY

2. INVENTORY

The following table summarizes the Company's inventory balances as of March 31, 2013 and December 31, 2012:

  March 31, December 31,
  2013 2012
       
  (in millions)
Coal, fuel oil and other raw materials $ 363 $ 373
Spare parts and supplies   392   393
Total $ 755 $ 766