Write a letter in 130-150 words.
关于第AG8432号信用证
贵方806号订单项下二十公吨小麦第AG8432号信用证已收到,金额为2960美元。
该证要求12月31日前交货。由于最早的一艘去贵港的船“和平”轮定于1月3日左右才离开上海，我方无法按贵方所确定的日期交货。
为此我方请求贵方将信用证装船期延至1月15日，并电报通知我方。我方知道电改信用证花费很大，但是此事我方无法控制。
此致
敬礼
2014年12月16日
【正确答案】：Dear Sirs,
We have received your Letter of Credit No. AG8432 for the amount of $ 2,960 to cover your order No. 806 for 20 metric tons of wheat.
The said credit calls for shipment on or before the 31st of December. As the earliest steamer sailing for your port is the S.S. "PEACE" scheduled to leave Shanghai on or about the 3rd of January, it is, therefore, impossible for us to effect shipment at the time you named.
This being the case,we have to ask you to be so kind as to extend the date of shipment to the 15th of January, under cable advice to us. We understand that cable amendment is costly, but this is a matter over which we can exercise no control.
Yours faithfully,
King Zhao
