5. Hal promises not to foreclose on a mortgage that he holds on an office complex that Christopher owns. In reliance on this promise, Christopher spends $200,000 to remodel the complex. Which of the following is correct with regard to Hal's promise? a. Hal's promise not to foreclose is unsupported by consideration. b. Hal's promise is noncontractual. c. Hal's promise may be enforced against him based upon the doctrine of promissory estoppel. d. All of the above