title: Variable not defined in AMPL
body: <p>I keep running into an error with AMPL wherein whenever I try to model my mod file I get an error: Y1 is already defined, this is first time I am using AMPL and not sure where I am going wrong, following is my code and I would really appreciate any help with this. I tried changing the variable name from Y1 to something else then I started getting same error with other variable:</p>
  
  <pre><code>#Creating Variables
  var Y1;
  var Y2;
  var Y3;
  #writing the objective fincations
  maximize Throughput:500 * Y1 + 450 * Y2 + 600 * Y3;
  #writing constraints
  subject to 1_limit: 8 * Y1 + 5 * Y2 + 8 * Y3 &lt;=60;
  subject to 2_limit: 10 * Y1 + 20 * Y2 + 10 * Y3 &lt;=150;
  subject to 3_limit: 0 &lt;= Y1 &lt;=8;
  </code></pre>