\begin{cofactors}
  $f$ \= $= ((\lnot a \lor b) \land (a \lor b))$\\
    \>$f_{b}$ \= $= \true$\\
    \>$f_{\lnot b}$ \= $= \false$\\
  \end{cofactors}
  The final ROBDD: 
  \begin{center}
  \scalebox{0.75}{
  
  \begin{tikzpicture}[>=latex,line join=bevel,]
    \pgfsetlinewidth{1bp}
  %%
  \pgfsetcolor{black}
    % Edge: f_E -> b0
    \draw [] (21.5bp,94.988bp) .. controls (21.5bp,84.921bp) and (21.5bp,69.474bp)  .. (21.5bp,59.304bp);
    % Edge: b0 -> 0
    \draw [] (19.503bp,36.791bp) .. controls (16.934bp,23.663bp) and (12.77bp,2.3815bp)  .. (12.513bp,1.0642bp);
    % Edge: b0 -> 1
    \draw [] (23.719bp,36.791bp) .. controls (26.573bp,23.663bp) and (31.2bp,2.3815bp)  .. (31.486bp,1.0642bp);
    \definecolor{strokecol}{rgb}{0.0,0.0,0.0};
    \pgfsetstrokecolor{strokecol}
    \draw (27.237bp,20.608bp) node {\Large$\bullet$};
    % Node: f_E
  \begin{scope}
    \definecolor{strokecol}{rgb}{0.0,0.0,0.0};
    \pgfsetstrokecolor{strokecol}
    \draw (43.0bp,117.0bp) -- (0.0bp,117.0bp) -- (0.0bp,95.0bp) -- (43.0bp,95.0bp) -- cycle;
    \draw (21.5bp,106.0bp) node {$f$};
  \end{scope}
    % Node: b0
  \begin{scope}
    \definecolor{strokecol}{rgb}{0.0,0.0,0.0};
    \pgfsetstrokecolor{strokecol}
    \draw (21.5bp,48.0bp) ellipse (11.0bp and 11.0bp);
    \draw (21.5bp,48.0bp) node {$b$};
  \end{scope}
  %
  \end{tikzpicture}
  
  
  }
  \end{center}