Answer:-only choose to stay if the additional benefits gained form the extra study session are greater than the additional cost of 30 mins more in class
Explanation:when it comes to studying it is of a high value if one can benefit more from any session they take and if that session can improve their knowledge or help them even more on other areas where they may still lack.
However if being in class has helped a student more than taking an extra class ,it will be good not to take an extra class which may accumulate unccessary if it doesn't add any value to their studying .