EL表達式求和與求積

<table border="1px solid" align="center">
        <tr>
            <td bgcolor="#6495ed">商品名稱</td>
            <td bgcolor="#6495ed">商品單價</td>
            <td bgcolor="#6495ed">購買數量</td>
            <td bgcolor="#6495ed">金額</td>
        </tr>
        <c:forEach items="${requestScope.carsList}" var="cars">
            <tr>
                <td>${cars.bookname}</td>
                <td>${cars.price}</td>
                <td>${cars.ordernumber}</td>
                //求出單價和數量的乘積
                <%--<td>${cars.ordernumber*cars.price}</td>--%>
                <td>${cars.totalprice}</td>
                //這裡通過周遊求和算出總計的價格
                <c:set var="total"  value="${total+cars.totalprice}"></c:set>
            </tr>
        </c:forEach>
        <tr>
            <td colspan="4" align="center">總計:${total}</td>
        </tr>
        <tr>
            <td align="center">收貨位址:<input type="text" name="address"></td>
        </tr>
        <tr>
            <td colspan="4" align="center">
                <a href="/shopIndexServlet">繼續購物</a>
                <a href="#" onClick="javascript :history.go(-1);">傳回購物車</a>
                <a href="/">确認購買</a>
            </td>
        </tr>
    </table>