An introductory statistics class has 400 students and their grades are approximately normally distributed with $\mu$= 250 points and $\sigma$=15 points out of a possible 300 points.
The following grading scale is used:
|Grade||% of Points Earned|
|A||92 - 100%|
|AB||88 - 91%|
|B||82 - 87%|
|BC||78 - 81%|
|C||65 - 77%|
|D||50 - 64%|
|F||40% and lower|
Alex earned $273$ points. What is her grade?
If necessary, use the table at: http://www.itl.nist.gov/div898/handbook/eda/section3/eda3671.htm.