VLM Food Trading International, Inc., a Canadian agricultural supplier, sold frozen potatoes to Illinois Trading Co., an American buyer and seller of produce. For each of their transactions, Illinois Trading sent a purchase order setting out the terms, and VLM responded with a confirming e-mail. VLM then shipped the order, Illinois Trading accepted it, and VLM followed up with a "trailing" invoice. Only the trailing invoice included a provision that the buyer would be liable for attorneys' fees if it breached the contract. Nine transactions occurred without incident. Illinois Trading ran into financial difficulties, however, and did not pay for the next nine shipments. VLM filed a suit in a federal district court against the buyer, seeking to recover the unpaid amount plus attorneys' fees. Illinois Trading admitted that it owed the price for the potatoes but contested liability for the attorneys' fees. A federal appellate court agreed with Illinois Trading that under the CISG, the attorneys' fee provision in the trailing invoice did not become part of the parties' contract. The attorneys' fee provision was a material alteration to the contract terms, and Illinois Trading did not agree to the additional term.

Note: Can you please answer this question using IRAC( Issue, Rule of Law, Analysis, and Conclusion) format. Because then it will be easy for me to understand the case a a lot better.