|                                                       |   | Year Ended December 31, |   |
|------------------------------------------------------------|--------|------------------------------|--------|
|                                                       |   | 2006                         |   |   | 2007 (1) |   |   | 2008 (1) |   |   | 2009 (1) |   |   | 2010 (1) |   |
|                                                       |   |                         |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Net Income                                                 |   | $                            | 271    |   |   | $ | 273 |   |   | $ | 222 |   |   | $ | 208 |   |   | $ | 200 |   |
| Income taxes                                               |   |                         | 132    |   |   |   | 126 |   |   |   | 121 |   |   |   | 102 |   |   |   | 116 |   |
| Capitalized interest                                       |   |                         | (4     | ) |   |   | (10 | ) |   |   | (7 | ) |   |   | (3 | ) |   |   | (3 | ) |
|                                                       |   |                         | 399    |   |   |   | 389 |   |   |   | 336 |   |   |   | 307 |   |   |   | 313 |   |
|                                                       |   |                         |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Fixed charges, as defined:                                 |   |                         |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
|                                                       |   |                         |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Interest                                                   |   |                         | 240    |   |   |   | 230 |   |   |   | 245 |   |   |   | 289 |   |   |   | 289 |   |
| Capitalized interest                                       |   |                         | 4      |   |   |   | 10 |   |   |   | 7 |   |   |   | 3 |   |   |   | 3 |   |
| Interest component of rentals charged to operating expense |   |                         | 2      |   |   |   | 1 |   |   |   | 2 |   |   |   | ─ |   |   |   | ─ |   |
| Total fixed charges                                        |   |                         | 246    |   |   |   | 241 |   |   |   | 254 |   |   |   | 292 |   |   |   | 292 |   |
|                                                       |   |                         |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Earnings, as defined                                       |   | $                            | 645    |   |   | $ | 630 |   |   | $ | 590 |   |   | $ | 599 |   |   | $ | 605 |   |
|                                                       |   |                         |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Ratio of earnings to fixed charges                         |   |                         | 2.62   |   |   |   | 2.61 |   |   |   | 2.32 |   |   |   | 2.05 |   |   |   | 2.07 |   |

|   | (1) | Excluded from the computation of fixed charges for the years ended December 31, 2007, 2008, 2009 and 2010 is interest expense of $4 million, $7 million, $1 million and $8 million, respectively, which is included in income tax expense. |
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