求翻译：支付方法：凭100%保兑的，不可撤销的。可转让的、可分割的、于装运前30天送达卖方的、装运后30天在中国保持议付有效的、金额为2万美元的即期信用证。是什么意思？

Payment method: With 100% confirmation, irrevocable. Transferable, divisible, served 30 days prior to shipment, the seller, 30 days after shipment in China remain valid for negotiation in the amount of $ 20,000 letter of credit at sight.

Payment methods: By 100 per cent of the US dollar warranty, and cannot be undone. You can transfer, can be split, the 30 days prior to shipment to the seller, the shipping of the 30 days after the payment in China remains valid, the amount of $20,000 for the credit.

Payment method: Depends on 100% to guarantee cashing, cannot be abolished.Rotatable lets, be possible to divide, 30 days delivers the seller before shipping, ships latter 30 day in the Chinese maintenance negotiation effectively, the amount is 20,000 US dollar immediate letters of credit.

Payment methods: 100% confirmed, irrevocable. Transferable, divisible, and served 30 days prior to shipment, shipment by the seller 30 days of negotiation in China remain effective, the amount of 20,000 dollar letter of credit at sight.

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