reserve V for non empty set,
  A,B,A9,B9 for Element of V;
reserve f,f9 for Element of Funcs(V);
reserve m,m1,m2,m3,m9 for Element of Maps V;
reserve a,b for Object of Ens(V);
reserve f,g,f1,f2 for Morphism of Ens(V);

theorem
  for W being Universe, a,b being Object of Ens(W) st Hom(a,b) <> {}
  for f being Morphism of a,b st f is epi holds @f
  is surjective
proof
  let W be Universe, a,b being Object of Ens(W) such that
 Hom(a,b) <> {};
  let f be Morphism of a,b;
  {} in W & {{}} in W by CLASSES2:56,57;
  then
A1: {{},{{}}} in W by CLASSES2:58;
  {} in {{},{{}}} & {{}} in {{},{{}}} by TARSKI:def 2;
  hence thesis by A1,Th36;
end;
