Joe Was a Contractor and He Hired Subtrades to Help

Joe was a contractor and he hired subtrades 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,Joe's suppliers increased the cost of lumber,and Joe told Sam that he could no longer pay him the amount on which they'd 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-upon price for the last two jobs.Sam sued Joe for the original contract price,claiming that he'd received no consideration for his agreement to take less for the last two jobs.Explain what defences may be available to Joe under these circumstances and his likelihood of success.