reserve x, y for object, X, X1, X2 for set;

theorem Th6:
  N_Funcs(X) is Subset of N_PFuncs(X)
proof
  N_Funcs(X) c= N_PFuncs(X)
  proof
    let x be object;
    assume x in N_Funcs(X);
    then x is Function of X,NAT by Def19;
    hence thesis by Def18;
  end;
  hence thesis;
end;
