某公司于9月8日收到美国A公司就出售化工产品(AA)发来的电文： “OFFER COMMODITY AA ART．101 5000M／T IN BULK USD 3500 PER M／T FOB NEW YORK NOV．SHIPMENT BY IRREVOCABLE LETTER OF CREDIT PAYABLE AT SIGHT PLEASE REPLY REACHING US SEPT．12TH．” 我方接电后，经研究，于9月11日上午10时去电如下： “YOURS 8TH ACCEPT PLEASE SEND YOUR CONTRACT IMMEDIATELY．” 当天上午11点，我 公司业务员收到A公司电文如下： “WE HAVE RECEIVED YOUR FAX JUST NOW BUT WE ARE VERY SORRY THAT OUR OFFER HAS BEEN REVOKED BECAUSE THE DEMAND IS BRISK AND THE GOODS HAS SOLD OUT．” 试分析上述电文，并指出双方是否成立了合同关系。为什么?