TIMED On two examinations, you have the grade 88 and 91. There is an optional final examination, which counts as one grade. You decide to take the final in order to get a course grade of A, meaning a final average of at least 90.
A. What must you get on the final exam to earn an A in the course?
B. By taking the final, if you do poorly, you must risk the B that you have in the course based on the first two exam grades. If your final average is less than 80, you will lose your B in the course. Describe the grades on the final exam that will cause this to happen.

a. You must get at least a ___
b. You will lose your grade if you get less than a ___