|                                                                                             |
|---------------------------------------------------------------------------------------------|
|                                                                                             |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
|                                                                                        |   | Three Months Ended |   | Year Ended |
|                                                                                        |   | March 31, |   | December 31, |
|                                                                                        |   | 2013 |   | 2012 |   | 2011 |   | 2010 |   | 2009 |   | 2008 |
| (millions)                                                                                  |   |   |   |   |   |   |   |   |   |   |   |   |
| Income (Loss) From Continuing Operations Before Income Tax and Income From Equity Investees |   | $ | 258 |  |   | $ | 1,170 |  |   | $ | 309 |  |   | $ | 730 |  |   | $ | (410 | ) |   | $ | 1,598 |  |
| Add (Deduct)                                                                                |   |   |   |   |   |   |   |   |   |   |   |   |
| Fixed Charges                                                                               |   | 71 |  |   | 288 |  |   | 207 |  |   | 148 |  |   | 136 |  |   | 109 |  |
| Capitalized Interest                                                                        |   | (42 | ) |   | (151 | ) |   | (132 | ) |   | (67 | ) |   | (45 | ) |   | (33 | ) |
| Distributed Income From Equity Investees                                                    |   | 28 |  |   | 204 |  |   | 225 |  |   | 139 |  |   | 92 |  |   | 221 |  |
| Earnings as Defined                                                                         |   | $ | 315 |  |   | $ | 1,511 |  |   | $ | 609 |  |   | $ | 950 |  |   | $ | (227 | ) |   | $ | 1,895 |  |
|                                                                                        |   |   |   |   |   |   |   |   |   |   |   |   |
| Net Interest Expense                                                                        |   | 25 |  |   | 125 |  |   | 65 |  |   | 72 |  |   | 84 |  |   | 69 |  |
| Capitalized Interest                                                                        |   | 42 |  |   | 151 |  |   | 132 |  |   | 67 |  |   | 45 |  |   | 33 |  |
| Interest Portion of Rental Expense                                                          |   | 4 |  |   | 12 |  |   | 10 |  |   | 9 |  |   | 7 |  |   | 7 |  |
| Fixed Charges as Defined                                                                    |   | $ | 71 |  |   | $ | 288 |  |   | $ | 207 |  |   | $ | 148 |  |   | $ | 136 |  |   | $ | 109 |  |
|                                                                                        |   |   |   |   |   |   |   |   |   |   |   |   |
| Ratio of Earnings to Fixed Charges                                                          |   | 4.4 |   | 5.2 |   | 2.9 |   | 6.4 |   | — |  |   | 17.4 |
|                                                                                        |   |   |   |   |   |   |   |   |   |   |   |   |
| Amount by Which Earnings Were Insufficient to Cover Fixed Charges                           |   | $ | — |  |   | $ | — |  |   | $ | — |  |   | $ | — |  |   | $ | (363 | ) |   | $ | — |  |