55. William agrees to drill a well up to 200 feet deep for John's rural cabin. The contract price is $3,000. After drilling 100 feet, William strikes solid granite rock. He talks to John and explains that this is highly unusual for the area and could not have been anticipated at the time of entering into the contract. He offers to get a special drill, but says it will cost him more money, so that he will be unable to complete the project for the agreed price. Because John is anxious to have the well, he agrees to pay William an additional $1,000 to complete the job. However, once the well is finished, he changes his mind and now says he will pay only the originally agreed-upon amount.
a. The parties have agreed to a substitute contract which discharges the original contract. John is obligated to pay the additional $1,000.