Tinker Construction had a contract with Scroge to build a factory addition for Scroge by a particular date. The contract contained a penalty clause exacting daily penalties for late performance, and Tinker was working hard to complete the building on time. Because prompt completion of the addition was so important to Scroge, however, Scroge offered Tinker a bonus if it completed the factory addition on time. Scroge also learned that the supplier of parts for machinery that he had contracted for had called and said that it could not deliver the parts on Scroge's schedule for the price it had agreed to. Because there was no other supplier, Scroge promised to pay the requested higher price. The factory addition was completed on time and the parts arrived on time. Scroge then refused to pay both the bonus to Tinker and the higher price for the parts. Were these promises enforceable?