输入的总值达到50后，如何启用提交按钮？

Question

I am trying to enable the submit button after the total value of my fields reaches 50. Each field has a different quantity value, the first one is 5, the second 10 and the third 25. When The user inputs a number it is multiplied by the quantity and then added to the total. I am trying to enable the submit button once the total reaches 50. I tried to use a key up function to change the disabled value of the button that targets the total but nothing seems to work. I stripped out the code that doesnt work, so now I am back at square one.

Here is the fiddle

http://jsfiddle.net/mdiadmin/TJ7VL/1/

HTML:

<table>
<tr>
    <th>How many units did you sell?</th>
    <th></th>
    <th></th>
</tr>
<tr class="txtMult">
    <td>
        <input name="txtEmmail" class="val1" />
    </td>
    <td> <span class="val2">How many ball joints? (5 laps per unit)</span>

    </td>
    <td></td>
</tr>
<tr class="txtMult">
    <td>
        <input name="txtEmmail" class="val1" />
    </td>
    <td> <span class="val3">How many struts? (10 laps per unit)</span>

    </td>
    <td></td>
</tr>
<tr class="txtMult">
    <td>
        <input name="txtEmmail" class="val1" />
    </td>
    <td> <span class="val4">How many total undercar assemblies? (25 laps per unit)</span>

    </td>
    <td></td>
</tr>
<tr>
    <td colspan="3" align="left">Total Laps <span id="grandTotal">0.00</span>
        <br>
        <input id="sbmt" type="submit" name="Submit" value="Submit" disabled> 
    </td>
</tr>
</table>

Javascript:

$(document).ready(function () {
  $(".txtMult input").keyup(multInputs);

  function multInputs() {
      var mult = 0;
      // for each row:
      $("tr.txtMult").each(function () {
          // get the values from this row:
          var $val1 = $('.val1', this).val();
          var $val2 = 5;
          var $val3 = 10;
          var $val4 = 25;
          var $total = ($val1 * 1) * ($val2 * 1)
          $('.multTotal',this).text($total);
          mult += $total;
      });
      $("#grandTotal").text(mult);
  }
});

Answer 1

       if (mult >= 50){
           $("#sbmt").removeAttr("disabled");
       }
       $("#grandTotal").text(mult);

Answer 2

I suppose you would like to disable the button after the value is once again under the threshold:

$(document).ready(function () {

  $(".txtMult input").keyup(multInputs);
  var submitButton = $('#sbmt');
  var grandTotal = $("#grandTotal");

  function multInputs() {
      var mult = 0;
      // for each row:
      $("tr.txtMult").each(function () {
          // get the values from this row:
          var $val1 = $('.val1', this).val();
          var $val2 = 5;
          var $val3 = 10;
          var $val4 = 25;
          var $total = ($val1 * 1) * ($val2 * 1)
          $('.multTotal',this).text($total);
          mult += $total;
      });


      if(mult >= 50) {
        submitButton.removeAttr('disabled');
      } else {
        submitButton.attr('disabled', 'disabled');
      }


      grandTotal.text(mult);
  }
});