Mass of man = 40 kg   , g = 10 m/s^2

Frictional force is developed b/w hands,  legs & block side with the wall by the weight of man. So he remains in equilibrium .

He gives equal force on both the walls so he gets equal reaction from both the walls. If he applies unequal forces R that should be different because he can't rest b/w the walls.

Frictional force = 2R to balance his weight.

   R + R = 40g

    2R = 40 * 10

        R = 400 / 2 * 0.8

           = 250 N

 

( b ) Normal force = 250 N