The following table summarizes information relating to our long-term debt, which we collectively refer to as our Senior Notes (in millions, except interest rates):

		April 24, 2020			April 26, 2019
	Effective Interest Rate	Amount			Amount
2.00% Senior Notes Due September 2019	2.32%	$	—		$	400
3.375% Senior Notes Due June 2021	3.54%		500			500
3.25% Senior Notes Due December 2022	3.43%		250			250
3.30% Senior Notes Due September 2024	3.42%		400			400
Total principal amount			1,150			1,550
Unamortized discount and issuance costs			(4	)		(6	)
Total senior notes			1,146			1,544
Less: Current portion of long-term debt			—			(400	)
Total long-term debt		$	1,146		$	1,144

Our $400 million, 3.30% Senior Notes, were issued in September 2017 with interest paid semi-annually in March and September. Our 3.375% Senior Notes and 3.25% Senior Notes, with principal amounts of $500 million and $250 million, respectively, were issued in June 2014 and December 2012, respectively. Interest on these Senior Notes is paid semi-annually in June and December. Our Senior Notes, which are unsecured, unsubordinated obligations, rank equally in right of payment with any existing and future senior unsecured indebtedness. On September 27, 2019, we paid $400 million to extinguish our 2.00% Senior Notes at maturity.

We may redeem the Senior Notes in whole or in part, at any time at our option at specified redemption prices. In addition, upon the occurrence of certain change of control triggering events, we may be required to repurchase the Senior Notes under specified terms. The Senior Notes also include covenants that limit our ability to incur debt secured by liens on assets or on shares of stock or indebtedness of our subsidiaries; to engage in certain sale and lease-back transactions; and to consolidate, merge or sell all or substantially all of our assets. As of April 24, 2020, we were in compliance with all covenants associated with the Senior Notes.

As of April 24, 2020, our aggregate future principal debt maturities are as follows (in millions):

We have a commercial paper program (the Program), under which we may issue unsecured commercial paper notes. Amounts available under the Program, as amended on July 17, 2017, may be borrowed, repaid and re-borrowed, with the aggregate face or principal amount of the notes outstanding under the Program at any time not to exceed $1.0 billion. The maturities of the notes can vary, but may not exceed 397 days from the date of issue. The notes are sold under customary terms in the commercial paper market and may be issued at a discount from par or, alternatively, may be sold at par and bear interest at rates dictated by market conditions at the time of their issuance. The proceeds from the issuance of the notes are used for general corporate purposes. As of April 24, 2020 and April 26, 2019, we had commercial paper notes outstanding with an aggregate principal amount of $523 million and $249 million, respectively, weighted-average interest rates of 2.01% and 2.73%, respectively, and maturities primarily less than three months. During fiscal 2020, we received proceeds of $111 million from the issuance, and made repayments of $10 million for the settlement, of commercial paper notes with original maturities greater than three months.

In connection with the Program, we have a senior unsecured credit agreement with a syndicated group of lenders that expires on December 10, 2021. The credit agreement, as amended on July 17, 2017, provides a $1.0 billion revolving unsecured credit facility, with a $50 million letter of credit sub-facility, that serves as a back-up for the Program. Proceeds from the facility may also be used for general corporate purposes to the extent that the credit facility exceeds the outstanding debt issued under the Program. The credit agreement includes options that allow us to request an increase in the facility of up to an additional $300 million and to extend its maturity date for two additional one-year periods, both subject to certain conditions. As of April 24, 2020, we were in compliance with all associated covenants in this agreement. No amounts were drawn against this facility during any of the periods presented.

In fiscal 2016, we entered into a sale-leaseback arrangement of certain of our land and buildings, under which we leased back certain of our properties rent free over lease terms ending at various dates through December 31, 2017. These properties did not qualify for sale-leaseback accounting and as a result they were accounted for as financing transactions. During fiscal 2018, we terminated leases under the arrangement and recorded a non-cash sale of properties with a net book value of $54 million, the extinguishment of $130 million in financing obligations, and a gain of $76 million. There are no balances remaining on our consolidated balance sheets as of April 24, 2020 or April 26, 2019 associated with this sale-leaseback arrangement.