You are pressing mass M = 0.908 kg against a vertical wall with a horizontal force F of magnitude F = 6.36 N, and the mass remains at rest.
HINT: Draw a freebody diagram for this problem.
a) Find f, the magnitude of the force of static friction exerted by the wall on the block.
b) You now slowly decrease the horizontal force, and discover the block just begins to slide when the applied force F has magnitude F = 5.01 N. Find μs, the coefficient of static friction between the wall and the block.