On December 1, Petro, Inc., sent Rachel & Rico (R&R) a letter, via overnight delivery, offering to employ R&R to review Petro’s tax situation for the current year for $10,000. In the letter, the company stated that R&R had ten days to accept. On December 5, R&R sent an e-mail message that stated, "The price for the tax analysis seems too low. Would you consider paying $15,000?" Petro received the message without responding immediately. The next day, Smith & Taylor, an R&R competitor, offered to conduct the appraisal for $8,000. On learning of this offer, R&R immediately e-mailed Petro, agreeing to do the work for $10,000. Petro received this message on December 7. Explain why R&R and Petro do, or do not, have a contract.