reserve U for Universe;
reserve x for Element of U;
reserve U1,U2 for Universe;

theorem
  for C,D being CategorySet st C is U-set & D is U-set holds
  Functors(C,D) is U-set
  proof
    let C,D be CategorySet;
    assume that
A1: C is U-set and
A2: D is U-set;
    SetToCat C is U-element & SetToCat D is U-element by A1,A2,Th89;
    then Functors(SetToCat C,SetToCat D) is U-element by Th72;
    hence thesis by Th88;
  end;
