The used car to Jonah, represents the concept known as Opportunity Cost.
This refers to the benefits that we would have gotten if we picked the next best alternative to the course of action we took.
Jonah's next best alternative to saving for college is buying the used car so the used car is the opportunity cost of saving for college.
In conclusion, the used car is an opportunity cost.
Find out more on opportunity costs at https://brainly.com/question/1549591.