total.php - before		total.php - after
1	function total ( $rows ) {	1	function total ( $rows, $tax = 0.21 ) {
2		2
3	$sum = 0;	3	$sum = 0;
4		4
5	foreach ( $rows as $row )	5	foreach ( $rows as $row )
6	$sum += $row ['price'];	6	$sum += $row ['price'] * $row ['quantity'];
7		7
8	return $sum;	8	return round ( $sum * ( 1 + $tax ), 2 );
9		9
10	}	10	}