From Mechanics

Using part a, we see from the figure that

\displaystyle F=S=\frac{98}{\tan \theta } and \displaystyle R=196

\displaystyle \begin{align} & F\le \mu R \\ & \frac{98}{\tan \theta }\le 0\textrm{.}6\times 196 \\ & \tan \theta \ge \frac{98}{0\textrm{.}6\times 196} \\ & \theta \ge 39\textrm{.}8{}^\circ \\ \end{align}