请将下列内容翻译。 THE BUYER SHOULD OPEN THROUGH A BANK ACCEPTABLE TO THE SELLER AN IRREVOCABLE LETTER OF CREDIT PAYABLE AT 30 DAYS AFTER THE BILL OF LADING DATE TO REACH THE SELLER 45 DAYS BEFORE THE MONTH OF SHIPMENT AND REMAIN VALID FOR NEGOTIATION IN CHINA UNTIL THE 15TH DAY AFTER THE DATE OF SHIPMENT.