Question $2$: Two Masses with Static Friction and Pulley

Problem: A system consists of two masses, $m_1=4\mathrm{.}0kg$ and $m_2=6\mathrm{.}0kg,$ connected by a light, inextensible string passing over a frictionless pulley. Mass $m_1$ lies on a horizontal surface where the coefficient of static friction is ${}_s=0\mathrm{.}40,$ and mass $m_2$ hangs vertically.

a$)$ Determine the maximum force of static friction that will prevent the system from moving.

b$)$ If the system is released from rest, calculate the acceleration of the masses assuming $m_2$ begins to move assuming ${}_k=0\mathrm{.}30.$