Problem with Quit command in menu: file does not exist

[Andrew Conkling]

I have a customised menu in ~/.xfce4/ that I'm using.  I tried setting
the visible to "yes" for Quit, but it doesn't work, just freezes the
desktop so I can't click on it anymore.  

<builtin name="Quit" cmd="quit" visible="yes"/>

There's no quit in my path and a 'locate quit' doesn't give anything
even related to Xfce.  Why don't I have that command installed or
alternatively, what's the command used for the quit button on the
taskbar?