      ERROR: failed to find symbol 'Xb' in AMPL parse info 
      ERROR: failed to find symbol 'Xc' in AMPL parse info 
      ERROR: failed to find symbol 'Xf' in AMPL parse info 
      ERROR: failed to find symbol 'SXb' in AMPL parse info 
      ERROR: failed to find symbol 'Xd' in AMPL parse info 
      ERROR: failed to find symbol 'Xe' in AMPL parse info 
