I use the following Latex script
\documentclass{article}
\usepackage{tikz,xcolor}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}
\filldraw[fill=gray!40!white, draw=black] (0,0) rectangle (4,2);
\node[black](dot) at (2,1) {\textbullet};
\node[below=0cm of dot] {\small{$x_a = (2,1)$}};
\end{tikzpicture}
\end{document}
To get:
Is there a way to add the corner coordinates as well? For example, I would like to see (0,0) in the lower-left corner.


