$discount = 
$cart_fields[$sc_cart_index_of_product_discount];

     if ($discount == "40+15")
      {
       $discount = 49;
      }
     else
      {
       if ($quantity >= 5)
        {
         $discount = ($discount+3);
         if ($quantity < 10)
          {
          $discount = ($discount-1);
          }
        }           
      }