The Following Table Shows the Age Distribution of a Sample

The following table shows the age distribution of a sample of 180 students at a local college.
AGE DISTRIBUTION OF 180 STUDENTS AT A LOCAL COLLEGE
$\begin{array}{|c|r|}\hline \text { Age Category } & \text { Number of students } \\\hline 15-19 & 36 \\\hline 20-24 & 44 \\\hline 25-29 & 60 \\\hline 30-34 & 38 \\\hline 35-39 & 2 \\\hline \text { Total } & 18 \\\hline\end{array}$
a. Of the students in the sample, what percentage is younger than 20 years of age?
b. What percentage is at least 30 years of age?
c. Based on this sample, what percentage of the students at the college do you estimate to be younger than 25 years of age?