We estimate that existing cash and cash equivalent balances, cash flows from operations, bank credit lines, and trade credit are adequate to meet our operating cash needs and to fund our planned capital investments, repayment of debt, common stock repurchases, and quarterly dividend payments for at least the next twelve months.
The table below presents our significant contractual obligations as of November 3, 2018:
1 - 3
3 - 5
Interest payment obligations
Operating leases (rent obligations)
New York buying office ground lease²
Total contractual obligations
1We have a $129.7 million liability for unrecognized tax benefits that is included in Other long-term liabilities on our interim Condensed Consolidated Balance Sheet. This liability is excluded from the schedule above as the timing of payments cannot be reasonably estimated except for the item disclosed in Note F.
²Our New York buying office building is subject to a 99-year ground lease.
Senior notes. As of November 3, 2018, we had outstanding unsecured 3.375% Senior Notes due September 2024 with an aggregate principal amount of $250 million. Interest on the 2024 Notes is payable semi-annually.
As of November 3, 2018, we also had outstanding two other series of unsecured senior notes in the aggregate principal amount of $150 million, held by various institutional investors. The Series A notes totaling $85 million are due in December 2018, and bear interest at 6.38%. The Series B notes totaling $65 million are due in December 2021, and bear interest at 6.53%. Borrowings under these senior notes are subject to certain financial covenants, including interest coverage and other financial ratios. As of November 3, 2018, we were in compliance with these covenants.
The 2024 Notes, Series A, and Series B senior notes are all subject to prepayment penalties for early payment of principal.
Off-Balance Sheet Arrangements
Operating leases. We currently lease all but two of our store locations. We also lease five warehouse facilities and two buying offices. In addition, we have a ground lease related to our New York buying office. Except for certain leasehold improvements and equipment, these leased locations do not represent long-term capital investments.
Two of our leased warehouses are in Carlisle, Pennsylvania with leases expiring in 2019 and 2020. A third warehouse is in Fort Mill, South Carolina, with a lease expiring in 2024. The fourth warehouse is in Rock Hill, South Carolina, with a lease expiring in 2028. The fifth warehouse is in Shafter, California, with a lease expiring in 2029. All of the warehouse leases contain renewal provisions.
We currently lease approximately 103,000 and 5,000 square feet of office space for our Los Angeles and Boston buying offices, respectively. The lease terms for these facilities expire in 2022 and 2020, respectively, and contain renewal provisions.
Purchase obligations. As of November 3, 2018, we had purchase obligations of approximately $3.0 billion. These purchase obligations primarily consist of merchandise inventory purchase orders, commitments related to construction projects, store fixtures and supplies, and information technology services, transportation, and maintenance contracts.
Standby letters of credit and collateral trust. We use standby letters of credit outside of our revolving credit facility in addition to a funded trust to collateralize our insurance obligations. As of November 3, 2018, February 3, 2018, and October 28, 2017, we had $7.3 million, $8.7 million, and $10.4 million, respectively, in standby letters of credit outstanding and $57.9 million,