1. The problem statement, all variables and given/known data;Given in the figure are two blocks A and B of weight 20 N and 100 N, respectively. These are being pressed against a wall by a force F 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 2. Relevant equations: f 1(static friction force acting on block A)=20 N=mass of A multiplied by g. 3. The attempt at a solution: Here f 2=f1+ m g B= 120 N The only thing I don't understand is why f1 is acting on block B?