\item Construct a Reduced Ordered Binary Decision Diagram (ROBDD) for the formula 

$$f = (p \land q) \lor (r \land s) \lor (\lnot p \land \lnot r)$$

using \textit{alphabetic variable order}. Use complemented edges and a node for \texttt{true} as the only constant node. To simplify drawing, you may assume that \textit{dangling edges} point to the constant node. Write down all cofactors that you compute to obtain the final result and mark them in the graph.
