\item \lect Consider the propositional formula $\varphi = \neg (\neg p
    \vee q) \rightarrow (p \wedge \neg r)$.

Find a propositional formula $\psi$ that is syntactically
    different from $\varphi$, but semantically equivalent to
    $\varphi$. Show the semantic equivalence of $\varphi$ and
    $\psi$ using truth tables.