tek hanede çarpma yapanı var banada çarpıp sabit bir sayıyı toplayan lazım ama bir türlü bulamadım 

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<body>
    <table>
        <tbody><tr>
            <th>Keşif</th>
            <th>Quantity</th>
            <th>Price</th>
            <th>Discount %</th>
            <th>Total Price</th>
        </tr>
        <tr>
            <td><input class="expensess top"  value="300" id="sayi1" ></td>
            <td><input class="expensess qty"></td>
            <td><input class="expensess price"></td>
            <td><input class="expensess discount" value="" ></td>
            <td><input class="expensess_sum" disabled="" id="sayi2" ></td>
        </tr>

        </tbody></table>
         <input type="text" id="sonuc">


</body>

<script>
  $('input.top,input.qty,input.price,input.discount').on('change keyup',function(){
  var $tr = $(this).closest('tr'),
      $top = $tr.find('input.top'),
      $qty = $tr.find('input.qty'),
      $price= $tr.find('input.price'),
      $discount= $tr.find('input.discount'),
      $total= $tr.find('input.expensess_sum'),
      $grand_total=$('#grand_total');

      $total.val($qty.val()*($price.val()));


})
</script>