The axis of the rocker arm of equal-shoulder scales, having a radius r, is inserted into the slot of the rack. With a weight of mass m on one cup and a load on the other, the rocker arm remains in a horizontal position. The weight of the rocker arm together with the cups is M, and the length of the rocker arm is 2L. How much can the weight of the load differ from the weight of the weight, if the coefficient of friction between the axis and the rack is equal to µ?