The systolic blood pressure (in mmHg ) of 60 hypertensive patients is given below.
\begin{tabular}{|l|l|l|l|l|l|}
\hline \begin{tabular}{l}
Systolic blood \\
pressure \\
\( (\mathrm{mmH} \mathrm{H}) \)
\end{tabular} & Frequency, \( \mathbf{f} \) & \begin{tabular}{l}
Cumulative \\
Frequency
\end{tabular} & \begin{tabular}{l}
Midpoint, \\
m
\end{tabular} & \( \mathbf{f m} \) & \( \mathrm{fm}^{2} \) \\
\hline \( 130<140 \) & 7 & 7 & 135 & 945 & 127575 \\
\hline \( 140<150 \) & 15 & B & 145 & 2175 & 315375 \\
\hline \( 150<160 \) & A & 48 & 155 & 4030 & 624650 \\
\hline \( 160<170 \) & 12 & 60 & C & 1980 & 326700 \\
\hline \( \boldsymbol{\Sigma} \) & 60 & & & & \\
\hline
\end{tabular}
The coefficient of variation (\%) is closest to:
A. 2
B. 12
c 6
D. 9