title: How to Change qty2 from var total = rate2 * qty2 Dynamicaly with select box?
body: <p>Let's say I have this HTML:</p>
  
  <pre><code>&lt;select id='list'&gt;
                          &lt;option value='qty2'&gt;Meter&lt;/option&gt;
                          &lt;option value='pcs2'&gt;Pcs&lt;/option&gt;
  </code></pre>
  
  <p> </p>
  
  <p>and then I have the js</p>
  
  <pre><code>  var rate2 = Number($("#rate_value_"+row).val());
    var qty2 = Number($("#qty_"+row).val());
    var pcs2 = Number($("#pcs_"+row).val());
    var total =  rate2 * qty2 
    total = total.toFixed(2);
    $("#amount_"+row).val(total);
    $("#amount_value_"+row).val(total);
  
    subAmount();
  
  } else {
    alert('no row !! please refresh the page');
  }
  </code></pre>
  
  <p>so i wanna change <code>var total = rate2 * this(selected from option value)</code>, can this be possible?</p>