Kate takes a part-time job and the sacrifice of study time causes her grade point average to fall from 3.5 to 2.9. Assume that the grade point average would have stayed at 3.5 if study time had not been reduced. The opportunity cost of having taken the job is the ________.a. cost of tuition b. 3.5 grade point average c. 0.6 decrease in the grade point average d. 2.9 grade point average e. money earned from the part-time job