Solve the all parts of given problem:
Problem: A 4.1 kg block is held at rest against a vertical wall by a horizontal force of 137 N.
Part A: What is the magnitude of the frictional force exerted by the wall on the block?
Part B: What is the magnitude of the minimum horizontal force needed to prevent the block from falling if the coefficient of friction between the wall and the block is µs = 0.4?
I need help to find the magnitude of the frictional force exerted by the wall on the block.