The principal amount of long-term debt, net of discount and debt issuance costs, is summarized as follows: | | | | | | | | | | | (in millions, except interest rate figures) | Interest Rate | | March 31,
2017 | | September 30,
2016 | Fixed-rate notes due: | | | | | | July 2019 | 5.25% | | $ | 300 |
| | $ | 300 |
| November 2021 | 3.10% | | 250 |
| | 250 |
| December 2023 | 3.70% | | 400 |
| | 400 |
| December 2043 | 4.80% | | 400 |
| | 400 |
| Variable-rate note due: | | | | | | December 2016 | 3 month LIBOR + 0.35% | | — |
| | 300 |
| Fair value swap adjustment (see Notes 13 and 14) | | | 15 |
| | 35 |
| Total | | | 1,365 |
| | 1,685 |
| Less unamortized debt issuance costs and discounts | | | 11 |
| | 11 |
| Less current portion of long-term debt | | | — |
| | 300 |
| Long-term Debt, Net | | | $ | 1,354 |
| | $ | 1,374 |
|
The new senior unsecured notes are summarized as follows: | | | | | | | (in millions, except interest rate figures) | Interest Rate | | Amount | Fixed-rate notes due: | | | | July 2019 | 1.95% | | $ | 300 |
| March 2022 | 2.80% | | 1,100 |
| March 2024 | 3.20% | | 950 |
| March 2027 | 3.50% | | 1,300 |
| April 2047 | 4.35% | | 1,000 |
| Total | | | 4,650 |
| Less unamortized debt issuance costs and discounts | | | 41 |
| Long-term Debt, Net | | | $ | 4,609 |
|
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