(Solved): On a sunny day, a dump truck driver slowly inclines the steel bed of his truck in order to unload so ...

On a sunny day, a dump truck driver slowly inclines the steel bed of his truck in order to unload some items. In the bed of the truck is a steel watering trough and a rubber tire.

At what angle of inclination ? does the watering trough begin to slide down the bed of the truck?

\begin{tabular}{|l|c|c|} \hline \multicolumn{1}{|c|}{ Materials } & Static ${?}_{\mathbf{s}}$ & Kinetic ${?}_{\mathbf{k}}$ \\ \hline Rubber on concrete & 1.00 & 0.80 \\ \hline Steel on steel (dry) & 0.80 & 0.60 \\ \hline Steel on steel (lubricated) & 0.10 & 0.05 \\ \hline Wood on wood & 0.50 & 0.20 \\ \hline Wood on snow & 0.12 & 0.06 \\ \hline Ice on ice & 0.10 & 0.03 \\ \hline \end{tabular}