Consider the following frequency distribution of the heights of 60 students of a class:
$$
\begin{array}{|l|l|}
\hline \text { Height (in cm) } & \text { No. of students } \\
\hline 150-155 & 15 \\
\hline 155-160 & 13 \\
\hline 160-165 & 10 \\
\hline 165-170 & 8 \\
\hline 170-175 & 9 \\
\hline 175-180 & 5 \\
\hline
\end{array}
$$
The sum of the lower limit of the modal class and upper limit of the median class is:
(a) 310
(b) 315
(c) 320
(d) 330