8B_How to Calculate The Salary

<html>
    <head>
    <title>If Statement</title>
    </head>
<body>
<form method="get"action=" ">
    Jumlah Jam Kerja <input type="text" name="jam" /><br/>
    <input type="submit" name="submit" value="submit" />
    <input type="reset" name="reset" value="reset" /><br/>
<?php
$jam = $_GET[jam];
$upah1 = 2000;
$upah2 = 3000;
$gaji1 = $jam * $upah1;
$lembur = ($jam - 48) * $upah2;
$gaji2 = (48 * $upah1) + $lembur;
echo "Jumlah Jam Kerja ".$_GET[jam]. " jam/minggu <br>";
if ($jam <= 48)
{
    echo "Gaji = Rp. ".$gaji1;
}
else if ($jam > 48)
{
    echo "Gaji Lembur = Rp. ".$gaji2;
}
?>
</form>
</body>
</html>