3 \usepackage{../graphics}

     3 \usepackage{../graphics}

     4 

     4 

     5 \begin{document}

     5 \begin{document}

     6 

     6 

     7 \section*{Homework 4}

     7 \section*{Homework 4}

     8 

    10 

     9 \begin{enumerate}

    11 \begin{enumerate}

    10 

    12 

    11 \item If a regular expression $r$ does not contain any occurrence of $\varnothing$,  

    13 \item If a regular expression $r$ does not contain any occurrence of $\varnothing$,  

    12 is it possible for $L(r)$ to be empty?

    14 is it possible for $L(r)$ to be empty?