\begin{center}
\begin{tikzpicture}[yscale=.8]
\node (omega) at (0,0) {$\Omega$};
\draw (omega) -- (2,2) node[right] (D) {$A$};
\draw (omega) -- (2,-2) node[right] (DB) {$\overline{A}$};

\draw (D) -- (4,3) node[right] (R1) {$B$};
\draw (D) -- (4,1) node[right] (R1B) {$\overline{B}$};

\draw (DB) -- (4,-1) node[right] (R2) {$B$};
\draw (DB) -- (4,-3) node[right] (R2B) {$\overline{B}$};

\node[above left] at ($0.5*(omega)+0.5*(D)$) {$0,35$};
\node[below left] at ($0.5*(omega)+0.5*(DB)$) {};
\node[above left] at ($0.5*(D)+0.5*(R1)$) {$0,35$};
\node[below left] at ($0.5*(D)+0.5*(R1B)$) {};
\node[above left] at ($0.5*(DB)+0.5*(R2)$) {$0,15$};
\node[below left] at ($0.5*(DB)+0.5*(R2B)$) {};
\end{tikzpicture}
\end{center}