Answer: The contract contains a subsequent condition
Explanation:
A subsequent condition is defined as something that ends something else. In the legal context, this means that it ends legal obligations or rights. In the case of Don, if he finds a new job out of state his contract should be discharged since he will not be present to use it. In these cases, the subsequent condition is present since, although Don's condition was not to move out of the state for a new job, if he finds it, he must leave since he will not be there to go to the gym and will be paying for a service that not using.
Although it is true that contracts that are carried out legally have their conditions and must be taken to the letter, there are exceptions where, depending on the nature of a situation, it cannot be fulfilled.