What is numerical value of coefficient of static friction

A block is resting on a wooden plank. There is a hinge on one end of the plank which allows the other end to be lifted to create an angle, θ, with respect to the horizontal as shown in the figure. The coefficient of static friction between the block and the plank is μs.

Part (a) Please select the correct Free Body Diagram, where Fg is the force due to gravity,FN is the normal force, and Fs is the static friction force.

Part (b) The angle θ is slowly increased. Write an expression for the angle at which the block begins to move in terms of θs.

Part (c) If a student measures that the block begins to move at an angle of θ = 31o, what is the numerical value of the coefficient of static friction, μs?