<file name="system/library/cart.php">
<operation><search position="after"><![CDATA[$option_price -= $option_value_query->row['price'];]]></search>
<add><![CDATA[ } elseif ($option_value_query->row['price_prefix'] == 'u') {
$option_price += ($option_price * $option_value_query->row['price']) / 100;]]></add>
</operation>
 </file>