The frequency $f$ of a spring with spring constant $k$ attached to a mass $m$ is
$\begin{align*}f = \frac{1}{2 \pi} \sqrt{\frac{k}{m}}\end{align*}$
If $k$ is doubled and $m$ is multiplied by $8$ , the $f$ will be divided by $2$ . Therefore, answer (C) is correct.

Solution to 2008 Problem 80