Joe was a contractor and hired sub trades to help build his houses. Sam was a framer and had agreed to frame four houses for Joe for a set price. Joe was to supply the materials. After two houses were completed, Joes suppliers increased the cost of lumber, and Joe told Sam that he could no longer pay him the amount that theyd agreed. Sam agreed to take 15% less for the other two jobs, which were then completed. During this time, regular payments were made from Joe to Sam, but the total amount received was 15% lower than the originally agreed on price for the last two jobs. Sam sued Joe for the original contract price, claiming that hed received no consideration for his agreement to take less for the last two jobs. In 350-500 words, explain what defences may be available to Joe under these circumstances and his likelihood of success.