Suppose your teacher finishes class 30 minutes early on the day before an exam. She indicates that you may leave, or you may stay on for an optional study period that will last for the remaining 30 minutes of the scheduled class time. You should:
A. Always choose to stay for the study period, since you have already paid for the class time.
B. Choose to stay only if you like the instructor, since the value obtained is higher than if you disliked the instructor.
C. Choose to stay only if the benefits gained from the extra study session exceed the cost of another 30 minutes in class.
D. Choose to stay for the study session only if you do not plan to study on your own for the exam.