The probabilities that a student will attain a $3.6 \mathrm{GPA}$, at least a $3.0 \mathrm{GPA}$, at least a $2.5 \mathrm{GPA}$, and at least a $2.0 \mathrm{GPA}$ are $.08, .47, .69$, and $.81$, respectively. Find the probabilities associated with each of the following.
a. A GPA worse than $3.0$ but greater than $2.5$
b. A GPA worse than $2.0$
c. A GPA of at least $2.5$
d. A GPA worse than $3.0$