A block of mass 4kg  is pressed against a wall by two perpendicular horizontal forces as shown in the figure. F1 is perpendicular to the wall and F2  is parallel to the wall. μs=0.8 , μk=0.5 and  g=10 m/s2For F1=75 N and  F2=30 N, the block remains at rest on the wall then the force of friction is