through (c) below.
\begin{tabular}{c|c|c}
\hline & Purchased Gum & Kept the Money \\
\hline Students Given Four Quarters & 26 & 16 \\
\hline Students Given a \$1 Bill & 15 & 28 \\
\hline
\end{tabular}
a. Find the probability of randomly selecting a student who spent the money, given that the student was given four quarters.
The probability is 0.619 .
(Round to three decimal places as needed.)
b. Find the probability of randomly selecting a student who kept the money, given that the student was given four quarters.
The probability is
(Round to three decimal places as needed.)

Step 1 ：The problem is asking for the conditional probability of a student keeping the money given that the student was given four quarters. From the table, we can see that the total number of students given four quarters is 26 + 16 = 42.

Step 2 ：Out of these 42 students, 16 students kept the money.

Step 3 ：Therefore, the probability of a student keeping the money given that they were given four quarters is calculated as \(\frac{16}{42}\).

Step 4 ：Using a calculator, we find that \(\frac{16}{42}\) is approximately 0.38095238095238093.

Step 5 ：Rounding to three decimal places, we get 0.381.

Step 6 ：Final Answer: The probability of randomly selecting a student who kept the money, given that the student was given four quarters is approximately \(\boxed{0.381}\).