reserve a,b,c,d,e for Real;
reserve X,Y for set,
          Z for non empty set,
          r for Real,
          s for ExtReal,
          A for Subset of REAL,
          f for real-valued Function;

theorem Th14:
  chi(X,Y) is bounded
  proof
    {0,1} c= [.0,1.] by Th13;
    then rng chi(X,Y) c= [.0,1.];
    hence thesis by Th12;
  end;
