Jenny’s average on 4 exams is Assuming she cannot earn more than 100 on any exam, what is the least she can earn on her 5th exam and still have a chance for an average of 84 after seven exams?

Jenny’s average on 4 exams is Assuming she cannot earn more than 100 on any exam, what is the least she can earn on her 5^th exam and still have a chance for an average of 84 after seven exams?