Answer full step by step

1. Students' marks on a test were normally distributed with a mean score of 70% and a standard deviation of S. a. What percent of students obtained a mark above 86%? (HINT: Use an expanded the z-score table.) b. What percent of students obtained a grade between 70% and 80%? 0. Determine the mark under which 75% of these students' marks occur. (This is known as the 75th percentile.)