急求翻译3句外贸合同中的句子，有50分

c）卖方银行出具的以买方为受益人不可撤销的质保金保函一份，保函金额为合同总价的10%。保函的有效期为货物验收合格后13个月。
The seller should provide a letter of guarantee for quality(如果是商品就用quality如果是服务就用performance或者execution) from the bank in favour of the buyer at which should be 10% of the total contract amount with a valid period of thirteen months after the acceptance of the goods(products).
如果由于非卖方的原因发货后六个月设备尚未安装，卖方可以仅凭上述的发票和保函议付信用证金额的10%。但并不免除卖方合同项下应承担的责任和义务。
If the installations of the equipments have not been initiated in six months after the delivery and not at the seller’s causes, the seller in such case could declare 10% of the negotiation credit amount based on the invoices and letter of guarantee hereinabove.
发货后，凭第11.1款所规定的装运单据议付信用证的90%，货到现场安装调试验收合格后，凭11.2条款议付其余10%。
As the sub-clause 11.1 specified after the delivery, the seller can declare 90% of the negotiation credit amount at the receipts of shipment. And after the acceptance of on-site delivery, installation and commissioning, the seller can de