A block A of mass 2kg rests on another block B of mass 8kg which rests on a horizontal floor. The coefficient of friction between A and B is 0.2 while that between floor and block B is 0.5 When a horizontal force is of 25N is applied on B,what is the force of friction between A and B?

As the block B, together with block A is laying on rough surface with u=0.5(u is not the initial velocity it is mu) it will be able to accelerate if the applied force is greater than u(mA+mB)g=0.5(10)(10)=50N. However , the force applied is only 25N .hence there will be no acceleration and frictional force between A & B will not arise . force between A and B is zero