Suppose your teacher finishes class 30 minutes early on the day before an exam. She indicates that you may leave, or stay on for an optional study period which will last for the remaining 30 minutes of the scheduled class time. You should:

You should only choose to stay if it's evident that, the additional benefits in the extra study session to be gained are greater than the additional cost to be acquired if you've chosen to study 30 minutes more in class.

In this kind of scenario, students are implored to focus more on what will be of benefit to them than any other thing i. e advantage over disadvantage