\documentclass{article}

% good old times
\usepackage{vaucanson-g}

\begin{document}

% first of all, we define our grid
\begin{VCPicture}{(0,-3)(6,3)}

% and then we create the states
\State[x]{(3,2)}{STATEA}
\State[s]{(0,0)}{STATEB}
\State[y]{(3,-2)}{STATEC}
\State[t]{(6,0)}{STATED}
% straight lines
\EdgeR{STATEB}{STATEA}{$c=5$}
\EdgeR{STATEB}{STATEC}{$c=2$}
\EdgeR{STATEA}{STATED}{$c=2$}
\EdgeR{STATEA}{STATEC}{$c=1$}
\EdgeR{STATEC}{STATED}{$c=4$}
\end{VCPicture}

\end{document}