Use the standard normal table in Appendix A to find the area a. At or below a

Question:

Use the standard normal table in Appendix A to find the area
a. At or below a point 1.64 standard deviations to the right of the mean.
b. At or below a point 2.33 standard deviations to the left of the mean.
c. In an interval starting 2.15 standard deviations to the left of the mean and ending .67 standard deviations to the right of the mean.