Given in the figure are two blocks A and B of weight 20N and 100N ,...

Given in the figure are two blocks $A$ and $B$ of weight $20N$ and $100N$, respectively. These are being pressed against a wall by a force $F$ and kept in equilibrium as shown. If the coefficient of friction between the blocks is $0 . 1$ and between block $B$ and the wall is $0 . 15$, the frictional force applied by the wall on block $B$ is: