The mean score on a school comprehensive assessment exam for fifth-graders was 87 points, with a standard deviation of 3.1 points. Results are normally distributed. a. What proportion of students scored less than 80 points? b. What proportion of students scored above 90 points? c. What proportion of students scored between 80 and 90 points? d. 10 percent of students had a score of greater than how many points?