| Schedule of Defined Benefit Plans Components of Expense Income |
The components of expense (income) for Pension Benefits and Other Retirement Benefits for the three and six months ended March 31, 2016 and 2015 are summarized as follows: | | | | | | | | | | | | | | | | | | Pension Benefits | | Other Retirement Benefits | | Three Months Ended | | Three Months Ended | | March 31 | | March 31 | (in millions) | 2016 | | 2015 | | 2016 | | 2015 | Service cost | $ | 3 |
| | $ | 3 |
| | $ | 1 |
| | $ | 1 |
| Interest cost | 31 |
| | 39 |
| | 2 |
| | 3 |
| Expected return on plan assets | (59 | ) | | (61 | ) | | (1 | ) | | (1 | ) | Amortization: | | | |
| | | | |
| Prior service credit | (1 | ) | | — |
| | — |
| | (1 | ) | Net actuarial loss | 20 |
| | 18 |
| | 2 |
| | 1 |
| Net benefit expense (income) | $ | (6 | ) | | $ | (1 | ) | | $ | 4 |
| | $ | 3 |
|
| | | | | | | | | | | | | | | | | | Pension Benefits | | Other Retirement Benefits | | Six Months Ended | | Six Months Ended | | March 31 | | March 31 | (in millions) | 2016 | | 2015 | | 2016 | | 2015 | Service cost | $ | 6 |
| | $ | 6 |
| | $ | 1 |
| | $ | 1 |
| Interest cost | 63 |
| | 78 |
| | 3 |
| | 4 |
| Expected return on plan assets | (119 | ) | | (121 | ) | | (1 | ) | | (1 | ) | Amortization: | | | | | | | | Prior service credit | (1 | ) | | (1 | ) | | — |
| | (2 | ) | Net actuarial loss | 39 |
| | 36 |
| | 4 |
| | 3 |
| Net benefit expense (income) | $ | (12 | ) | | $ | (2 | ) | | $ | 7 |
| | $ | 5 |
|
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