| (m) | Inventories |
Inventories, which consist primarily of consumable spare parts and supplies, are stated at cost less any applicable provision for obsolescence, and are charged to consolidated income statements when used in operations. Cost represents the average unit cost.
Inventories held for sale or disposal are carried at the lower of cost and net realizable value. Net realizable value is the estimated selling price in the ordinary course of business less the estimated costs of completion and the estimated costs necessary to make the sale.
When inventories are sold, the carrying amount of those inventories is recognized as an expense in the period in which the related revenue is recognized. The amount of any write-down of inventories to net realizable value and all losses of inventories are recognized as an expense in the period the write-down or loss occurs. The amount of any reversal of any write-down of inventories is recognized as a reduction in the amount of inventories recognized as an expense in the period in which the reversal occurs.