* Newton's Third Law: This law states that for every action, there is an equal and opposite reaction.

* Force Pairs: When the man pushes on the wall (action), the wall pushes back on him (reaction).

Therefore:

* Size: The wall exerts a force of 50 N on the man.

* Direction: The force exerted by the wall on the man is opposite to the direction he is pushing, meaning it's directed towards him.