Been having a hard time with this problem, can anyone help out?

Each year, thousands of college seniors take the Graduate Record Examination (GRE). Assume the scores are transformed so they have a mean of 600 and a standard deviation of 150. Furthermore, the scores are known to be normally distributed. Determine the percentage of students that score:

a. Between 650 and 825

b. 475 or greater

c. Below 750

d. Either less than 750 or more than 800