Elrod is attempting to introduce oral evidence in court to explain or modify the written contract he made with Weaver. Weaver has pleaded the parol evidence rule. In which of the following circumstances will Elrod not be able to introduce the oral evidence?

1. The modification asserted was made several days after the written contract had been executed.
2. The contract indicates that it was intended as the "entire contract" between the parties, and the point is covered in detail.
3. There was a mutual mistake of fact by the parties regarding the subject matter of the contract.
4. The contract contains an ambiguity on the point at issue.