A teacher informs her cell biology class (of 500+ students) that a test was very difficult, but the grades would be curved. Scores on the test were normally distributed with a mean of 37 and a standard deviation of 5. The maximum possible score on the test was 100 points. Because of partial credit, scores were recorded with 1 decimal point accuracy. (Thus, a student could earn a 37.6, but not a 36.77.) The grades are curved according to the following scheme. Find the numerical limits for each letter grade. Letter Scheme Interval A Top 15% B to C D F Scores above the bottom 74% and below the top 15% Scores above the bottom 26% and below the top 26% Scores above the bottom 15% and below the top 74% Bottom 15%