Wilson hired Great Value Homes to build his new house. He contracted for a Model #04L Floor Plan (one of the options offered by Great Value) with one modification, which was to move an interior wall two feet. Unfortunately, Great Value failed to make the modification when it built the house. The contract called for Wilson to pay $10,000 when the contract was signed, $30,000 when excavation started, and $60,000 upon completion. This payment arrangement was made as a matter of convenience and not because the payments corresponded to the amount of work done at the various stages. Wilson made the first two payments but refused to make the final payment when he realized that the wall was in the wrong place.