Harry enters a contract with Bill wherein Harry agrees to build a wooden deck onto Bill's house for $20,000. Harry draws the designs and provides the specifications for the deck. Harry agrees to have the deck finished within five weeks. After one week into the project, Harry goes back to Bill and says he cannot complete the deck as designed for less than $28,000. Bill is not pleased but agrees to pay Harry the additional $8000 for Harry to complete the deck. When Harry finishes building the deck, it is in full conformance with the design and specifications he had originally presented to Bill. Bill loves the deck and workmanship but refuses to pay Harry more than $20,000. Harry then sues Bill on his promise to pay the additional $8000. Who will prevail at trial? Discuss your reasons why.