This JQuery sum works in JSFiddler but not when try and open it in a browser? It must be something silly!

This JQuery sum works in JSFiddler but not when try and open it in a browser? It must be something silly!

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
                
</head>

<body>

<select class="quote" name="quote[50]">
    <option value="0">0</option>
    <option value="10">1</option>
    <option value="20">2</option>
    <option value="30">3</option>
    <option value="4">4</option>
    <option value="5">5</option>
</select>
<br>
<select class="quote" name="quote[51]">
    <option value="0">0</option>
    <option value="10">1</option>
    <option value="20">2</option>
    <option value="30">3</option>
    <option value="4">4</option>
    <option value="5">5</option>
</select>
    <br>
<select class="quote" name="quote[52]">
    <option value="0">0</option>
    <option value="10">1</option>
    <option value="20">2</option>
    <option value="30">3</option>
    <option value="4">4</option>
    <option value="5">5</option>
</select>
        <br>
         <br>

£<input id="sum" type="text" size="5" />

<script>
$(document).on('change', '.quote', function () {
    var total = 0;
    $('.quote').each(function () {
        total += parseFloat($(this).val());
    });
    $('#sum').val(total);
});
</script>

</body>
</html>