Three Objects Are Connected by Weightless Flexible Strings as Shown

Short Answer

Three objects are connected by weightless flexible strings as shown in the figure. The pulley has no appreciable mass or friction, and the string connected to the block on the horizontal bench pulls on it parallel to the bench surface. The coefficients of friction between the bench and the block on it are and You observe that this system remains at rest.
(a) Find the mass of the hanging object A.
(b) What is the magnitude of the friction force on the block on the bench?