Company A (China Company) sent an offer of 100MT goods to company B(US company): USD 2400 per MT CIF San Francisco, payable by letter of credit, shipment 2 months after the arrival of Letter of Credit, valid for 3 days. The next day company B replied: accept your offer, shipment immediately. A company did not respond. 2 days later, Company B opened a letter of credit through a bank in San Francisco with the content "shipment immediately". At that time the price of the product rose 20%, A company rejected to deliver the goods, rejected the letter of credit and declared the contract has not been arrived. There was a dispute between A and B. Who is right? Why