2D Rectangle Area

<?php

$x1 =floatval(readline());
$y1 =floatval(readline());
$x2 =floatval(readline());
$y2=floatval(readline());

$a = abs($x1 - $x2);
$b = abs($y1 - $y2);

$area = $a * $b;
$perimeter = 2*$a + 2*$b;

echo number_format($area,2,".","") .PHP_EOL;
echo number_format($perimeter,2,".","");