Caitlin's Science Professor Gives an a for an Average Of 85

Essay

Caitlin's science professor gives an A for an average of $85$ or better, and a B for an average of $75$ or better in her course. Caitlin has obtained scores of $84,71$ , and $77$ on her midterm examinations. If the final exam counts for as much as the three midterms together, what score must she get on her final exam to receive a B? To receive an A? (Assume that the maximum possible score on each test is $100$ .)