For a t-curve with df = 21, find each t-value, and illustrate your results graphically.
a. The t-value having area 0.10 to its right
c. The t-value having area 0.025 to its left (A t-curve is symmetric about 0.)
d. The two t-values that divide the area under the curve into a middle 0.90 area and two outside areas of 0.05