Answer:
Exchange and Unilateral Contract
Step-by-step explanation:
A unilateral is offer to the people of earning financial value in exchange of performing a particular task. The person Jack has announced the $100 reward for the person who will run a mile within one hour. This reward will be given to only those people who starts its performance and is a Unilateral contract. The semi done performance is not entitled for this reward and the only person eligible for this task would be the one who has completely performed the task.