For a normal distribution, a. what z-score separates the highest 25%

  

For a normal distribution,

a. What z-score separates the highest 25% from the rest of the scores?

b. What z-score separates the highest 60% from the rest of the scores?

c. What z-score separates the lowest 30% from the rest of the scores?

d. What z-score separates the lowest 80% from the rest of the scores?