Difficulty over a problem of friction about sleeve

How can I solve this problem below:

The asking problem:
A safety device used by workers climbing ladders fixed to high structures consists of a rail attached to the ladder and a sleeve which may slide on the flange of the rail. A chain connects the worker's belt to the end of an eccentric cam which may rotate about an axle attached to the sleeve at C. Determine the smallest allowable common value of the coefficient of static friction between the flange of the rail, the pins at A and B, and the eccentric cam if the sleeve is not  to slide down when the chain is pulled vertically downward.

Note: I included the sleeve drawing with this file.
The problem was taken from a book, so I had all the data for this problem.

Here I will give you the answer of this problem for your verification of your resolution:Coefficient of static friction = 0.0533