The components of net periodic benefit expense/(income) for our non-contributory qualified defined benefit pension plan (Primary Pension Plan), non-contributory supplemental pension plans and contributory postretirement health and welfare plan were as follows: | | | | | | | | | | Three Months Ended | ($ in millions) | May 2,
2015 | | May 3,
2014 | Primary Pension Plan | | | | Service cost | $ | 17 |
| | $ | 15 |
| Interest cost | 49 |
| | 53 |
| Expected return on plan assets | (89 | ) | | (87 | ) | Amortization of actuarial loss/(gain) | 26 |
| | 13 |
| Amortization of prior service cost/(credit) | 2 |
| | 1 |
| Net periodic benefit expense/(income) | $ | 5 |
| | $ | (5 | ) | | | | | Supplemental Pension Plans | | | | Service cost | $ | — |
| | $ | — |
| Interest cost | 2 |
| | 2 |
| Amortization of actuarial loss/(gain) | 3 |
| | 4 |
| Amortization of prior service cost/(credit) | — |
| | — |
| Net periodic benefit expense/(income) | $ | 5 |
| | $ | 6 |
| | | | | Primary and Supplemental Pension Plans Total | | | | Service cost | $ | 17 |
| | $ | 15 |
| Interest cost | 51 |
| | 55 |
| Expected return on plan assets | (89 | ) | | (87 | ) | Amortization of actuarial loss/(gain) | 29 |
| | 17 |
| Amortization of prior service cost/(credit) | 2 |
| | 1 |
| Net periodic benefit expense/(income) | $ | 10 |
| | $ | 1 |
| | | | | Postretirement Health and Welfare Plan | | | | Service cost | $ | — |
| | $ | — |
| Interest cost | — |
| | — |
| Amortization of actuarial loss/(gain) | — |
| | — |
| Amortization of prior service cost/(credit) | (2 | ) | | (2 | ) | Net periodic benefit expense/(income) | $ | (2 | ) | | $ | (2 | ) | | | | | Retirement Benefit Plans Total | | | | Service cost | $ | 17 |
| | $ | 15 |
| Interest cost | 51 |
| | 55 |
| Expected return on plan assets | (89 | ) | | (87 | ) | Amortization of actuarial loss/(gain) | 29 |
| | 17 |
| Amortization of prior service cost/(credit) | — |
| | (1 | ) | Net periodic benefit expense/(income) | $ | 8 |
| | $ | (1 | ) |
|