|                                                                          |   |                     |    |         |   |         | Twelve       |   |  Three  |   |
|-------------------------------------------------------------------------------|--------|--------------------------|---------|--------------|--------|--------------|--------------|--------|--------------|--------|
|                                                                          |   |                     |    |         |   |         |  Months |   |  Months |   |
|                                                                          |   | Years Ended December 31, |    |  Ended  |   |  Ended  |         |
|                                                                          |   | 2006                     |    | 2007         |   | 2008         |         |   | 2009         |   | 2010 |   |  3/31/2011 |   |  3/31/2011 |   |
| EARNINGS                                                                      |   |                |    |    |   |    |         |   |         |   |   |   |   |   |   |   |   |   |   |
| Income Before Income Taxes                                                    |   | $                        | 286,422 |         | $      | 387,473      |         | $      | 346,869      |   | $ | 415,382 |   | $ |  362,072 |   | $ | 381,834 |   | $ | 99,663 |   |
| Fixed Charges (as below)                                                      |   |                     | 74,155  |         |   | 86,900       |         |   | 109,245      |   |   | 109,152 |   |   |  102,104 |   |   | 99,926 |   |   | 23,816 |   |
| Total Earnings                                                                |   | $                        | 360,577 |         | $      | 474,373      |         | $      | 456,114      |   | $ | 524,534 |   | $  | 464,176 |   | $ | 481,760 |   | $ | 123,479 |   |
|                                                                          |   |                     |    |         |   |         |         |   |         |   |   |   |   |   |   |   |   |   |   |   |   |   |
| FIXED CHARGES                                                            |   |                     |    |         |   |         |         |   |         |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Interest Expense                                                              |   | $                        | 66,100  |         | $      | 69,625       |         | $      | 92,068       |   | $ | 88,184 |   | $  | 85,893 |   | $ | 83,857 |   | $ | 19,748 |   |
| Credit for Allowance for Borrowed Funds    Used During Construction |   |                     | 5,955   |         |   | 7,275        |         |   | 2,677        |   |   | 5,968 |   |   |  2,311 |   |   | 2,169 |   |   | 593 |   |
| Estimated Interest Element in Lease Rentals                                   |   |                     | 2,100   |         |   | 10,000       |         |   |  14,500 |   |   | 15,000 |   |   | 13,900 |   |   | 13,900 |   |   | 3,475 |   |
| Total Fixed Charges                                                           |   | $                        | 74,155  |         | $      | 86,900       |         | $      | 109,245      |   | $ | 109,152 |   | $  | 102,104 |   | $ | 99,926 |   | $ |  23,816 |   |
|                                                                          |   |                     |    |         |   |         |         |   |         |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Ratio of Earnings to Fixed Charges                                            |   |                     | 4.86    |         |   | 5.45         |         |   | 4.17         |   |   | 4.80 |   |   | 4.54 |   |   | 4.82 |   |   | 5.18 |   |