Blocks and Pulley on Inclined Plane III (bored yet?)

Two blocks with mass $M_1 = 5$ kg and $M_2 = 5$ kg are arranged as shown with $M_1$ sitting on an inclined plane and connected with a massless unstretchable string running over a massless, frictionless pulley to $M_2$, which is hanging over a drop. The two masses are released initially with $M_2$ 4 m above the ground. The inclined plane has a coefficient of static friction $\mu_s = 0.5$ and a coefficient of kinetic friction of $\mu_k = 0.25$.

a) Find an algebraic expression involving $M_1$, $M_2$, and $\mu_s$ from which one can find the largest angle $\theta_{\rm max}$ such that the system remains at rest. If you can solve this somewhat complicated expression, you will get some extra credit.

b) If $\theta = 37.5^\circ$ (so that it forms a 3-4-5 right triangle) and the top mass is ``nudged'' just enough to overcome static friction (if necessary) how fast is $M_2$ travelling when it hits the ground?