let e be Element of cB; :: thesis: e is Relation-like

per cases ( not cB is empty or cB is empty ) ;

suppose not cB is empty ; :: thesis: e is Relation-like

then e in cB ;
hence e is Relation-like ; :: thesis: verum

end;

suppose cB is empty ; :: thesis: e is Relation-like

hence e is Relation-like by SUBSET_1:def 1; :: thesis: verum

end;

end;