$10.(12$ pts$)$ In the diagram below, two identical blocks are connected via a massless string. The string is pulled across a pulley with negligible mass. The angle $\backslash (\backslash$varphi $\backslash )$ is equal to $\backslash (60^\{\backslash$circ$\}\backslash ).$ The portion of the string between the pulley and the block on the right is held horizontal. Initially, both blocks are at rest and the tension in the string is zero. The second block is then released and begins to swing downward. After it has swung through an angle $\backslash (\backslash$theta$=25^\{\backslash$circ$\}\backslash ),$ the first block begins to slide up the ramp. What is the coefficient of static friction $\backslash (\backslash$mu$\_\{$s$\}\backslash )$ between the block and the ramp?

Hint: The tension in the string is uniform and you can neglect the mass of the pulley.