system: You are a contract-analysis assistant performing a span-extraction task. You are given an excerpt from a commercial contract and the name of a clause type to locate within it.

Return the exact text of the requested clause, copied verbatim from the excerpt — identical wording and punctuation, with no paraphrasing, summarising, explanation, or added commentary.

The excerpt is one window of a much longer contract and often will not contain the requested clause. If the requested clause does not appear in this excerpt, respond with exactly: Not found.

Output only the extracted clause text, or the exact string `Not found.` — nothing else.

user: Contract excerpt:
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the SENDER shall have a limited capacity for shipment by the Pipeline of crudes of its own/production, subject to the existence of Available Capacity during the month of operation of the Service (hereinafter, the "Contracted Capacity"). 1.3 The scope of the obligations of ECOPETROL is limited to the reception, custody, shipment, decanting, and indispensable storage for the transportation and shipment of Crude to the SENDER. 1.4 The Contract hereof does not include the provision of the unloading service in unloading areas, the treatment of crudes, the storage in export terminals, or any terminal services. It is the responsibility of the SENDER to execute or contract these services whenever it may be necessary. The SENDER shall wave and hold ECOPETROL harmless for any damage or prejudice suffered by ECOPETROL as a result of failing to receive the Crude in the Exit Point, either by lack of the services before mentioned or by failing to provide the appropriate facilities for such purpose. 2 CLAUSE FIFTH FEES 5.1 The Contract is agreed under the "Spot" modality, understanding that the SENDER shall pay for the Barrels effectively transported through the Pipeline subject to the existence of Available Capacity in the Pipeline during the Month of Operation in which the Service is to be provided. 5.2 The SENDER is obliged irrevocably and unconditionally by subscription of this Contract to the payment of the fee indicated in the Specific Conditions for each Barrel effectively transported making use of its Contracted Capacity (hereinafter, the "Fee"). CLAUSE SIXTH READJUSTMENTS 6.1 The Monthly Fee agreed in this Contract shall be adjusted each year pursuant to the formula established by the Ministry of Mines and Energy in Resolution 124 386 of July 15th, 2010 or any provisions the amend, add or supersede it. CLAUSE SEVENTH TERMS OF PAYMENT 7.1 The SENDER undertakes the obligation to pay irrevocably and unconditionally the Service for the Contracted Capacity, twenty (20) calendar days at the latest, after ECOPETROL files in the offices of the SENDER the invoice for the provision of the Service. 7.2 ECOPETROL shall deliver to the SENDER on the twentieth (20) day of each month at the latest a preliminary account (invoice) with the amount that the SENDER must pay (corresponding to the current month) based on the Nomination made by the SENDER for the current month. 7.3 Considering that the charging for the Service is made on the Nomination of the current month, ECOPETROL in order to make the corresponding adjustment to the nominated volume and the volume of Crude actually shipped, shall generate the corresponding debit and credit vouchers and shall deliver said debit or credit vouchers together with the invoice(s) of the nominated month to be charged. The due date of the debit and credit vouchers shall be the same as for the invoice (with the nominated volume) of the current month in order to facilitate the SENDER the making of only one net payment for both items. 7.4 Payments shall be made in Colombian pesos using the arithmetic average of the representative market exchange rate certified by the Superintendence of Finance or the entity replacing it, of the days of the month corresponding to the Service invoiced. 7.5 The SENDER shall make the payment by means of making a deposit in any of the bank accounts as indicated by ECOPETROL. In case ECOPETROL requires any changes in the bank account, it shall be informed in writing to the SENDER. 7.6 The SENDER is obliged to receive the invoice once ECOPETROL has filed it. Any objections to the invoicing will not interrupt the term for the payment respect to the sums that are not objected by the SENDER, pursuant to the term established in this clause. ECOPETROL shall issue the note credit or equivalent document respect to the sums objected by the SENDER, in order to rectify the inaccuracy. 3 CLAUSE EIGHTH BONDS 8.1 The SENDER may pay in advance the Service for the Contracted Capacity, in which case the corresponding invoice shall be adjusted pursuant to the provisions in the Clause of Terms of Payment as it may apply. 8.2 Otherwise, In order to guarantee compliance with all and each of the obligations of the SENDER under the Contract hereof, including but without being limited to the payment of the Fee, the SENDER is obliged to constitute in favor of ECOPETROL and to deliver within ten (10) business days after the subscription of the Contract hereof for the amount indicated in the Specific Conditions (hereinafter, the "Bond"):
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Extract the exact clause related to "Irrevocable Or Perpetual License" from the excerpt above.