arithmetic operation with table column PDO - pdo

Question

I have a simple table with columns of price ,qty. cookeid and part_number.
I have managed somehow to convert my old mysql code to PDO but I need help to complete the 2nd stage.
To get the total price of sales for a customer, I need to choose every row
that has the customers cookie, then multiply qty and price for each row and finally add those values to get the total price.
I got the code that adds the columns together using Sum but don't know how to multiply the qty with each price and then add those together to get the grand total.
$rs = $pd->prepare('SELECT sum(price) FROM mcart WHERE cookieid=:cookie');
$rs->bindParam(':cookie',$_COOKIE[mcartId]);
$rs->execute();
$sum = $rs->fetchColumn();
echo "total price is ".$sum;

Answer 1

Solved it just in case anyone has similar problem.
$sql = "SELECT * FROM mcart";
$users = $pd->query($sql);
$totpr=0;
$totq=0;
foreach ($users as $row) {
// echo "price is: ".$row["price"] . "-". "quantity is: ".$row["qty"];
// ----- calculate total qty ------
$totq=$row["qty"];
$totqty=$totqty+$totq;
// ----- calculate total price ------
$totp=$row["qty"]*$row["price"];
$totpr=$totpr+$totp;
}
echo "Total qty is: ".$totqty;
echo "<br/>";
echo "Total price is: ".$totpr;
echo "<br/>";