fig019_is.pgf

% (c) 2012 Dimitrios Vrettos - d.vrettos@gmail.com
\begin{tikzpicture}[font=\small,x=10mm, y=10mm]

\draw[->] (0,0) -- (8,0) node [below right] () {$r$};

\foreach \x in {2,6}{
\draw(\x,3pt)--(\x,-3pt);
\begin{scope}[dotted]
\draw (\x,0) -- (\x,-2);
\draw (0,-.5) -- (2,-.5);
\draw (0,-1) -- (6,-1);
\end{scope}}

\node[above]  at (2,0) {$-21$};
\node[above]  at (6,0) {$\frac{27}{10}$};
\pattern[pattern= north east lines, pattern color=red] (6,-1.5) rectangle (8,-2);

\node[below] () at (7,-2) {$\IS$};

\begin{scope}[blue,thick]
\draw (2,-.5) -- (8,-.5);
\draw (6,-1) -- (8,-1);

\draw[fill=white] (2,-.5)circle (1.5pt);
\draw[fill=white] (6,-1)circle (1.5pt);

\end{scope}

\end{tikzpicture}