1- suppose students’ grades in statistics class have a symmetrical and bell-shaped distribution with a mean equal to 77 and a standard deviation of 6. answer the following questions and show your work: a. what is the percentage of grades that are less than 83? b. what is the percentage of grades that are greater than 65 and less than 89? c. what is the z-score for grade=70? d. what percentage of grades have a z-score of greater than 1?