What will be the output of the following PHP code?<?phpfunction

What will be the output of the following PHP code?

<?php
function calculation($Rs, $tax="")
    {
        $Result = $Rs + ($Rs * $tax);
        echo "$Result"; 
    }
calculation(80);	
?>

You can designate certain arguments as optional by placing them at the end of the list and assigning them a default value of nothing.