--- a/slides/slides02.tex	Thu Oct 01 22:10:00 2015 +0100
+++ b/slides/slides02.tex	Thu Oct 01 22:40:00 2015 +0100
@@ -165,6 +165,29 @@
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[c]
+\frametitle{Homework Question}
+
+\begin{itemize}
+\item Say \bl{$A = \{[a],[b],[c],[d]\}$}.\bigskip
+
+\begin{center}
+How many strings are in \bl{$A^4$}?
+\end{center}\bigskip\medskip\pause
+
+
+\begin{center}
+\begin{tabular}{l}
+What if \bl{$A = \{[a],[b],[c],[]\}$};\\ 
+how many strings are then in \bl{$A^4$}?
+\end{tabular}
+\end{center}
+\end{itemize}  
+
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
 \frametitle{The Star Operation}
 
 \begin{itemize}
@@ -238,9 +261,8 @@
          & \bl{$\mid$} & \bl{$r_1 + r_2$}      & alternative / choice\\
          & \bl{$\mid$} & \bl{$r^*$}            & star (zero or more)\\
   \end{tabular}
-  \end{textblock}
+\end{textblock}
   
-
 \end{frame}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%   
 
@@ -261,7 +283,8 @@
 \end{textblock}
 
 \begin{textblock}{6}(9,12)\small
-\bl{$L$} is a function from regular expressions to sets of strings\\
+\bl{$L$} is a function from regular expressions to 
+sets of strings\\
 \bl{$L$ : Rexp $\Rightarrow$ Set$[$String$]$}
 \end{textblock}
 
@@ -294,7 +317,7 @@
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[t]
-\frametitle{\begin{tabular}{c}Concrete Equivalences\end{tabular}}
+\frametitle{Concrete Equivalences}
 
 \begin{center}
 \bl{\begin{tabular}{rcl}
@@ -313,7 +336,7 @@
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[t]
-\frametitle{\begin{tabular}{c}Corner Cases\end{tabular}}
+\frametitle{Corner Cases}
 
 \begin{center}
 \bl{\begin{tabular}{rcl}
@@ -330,7 +353,7 @@
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{frame}[t]
-\frametitle{\begin{tabular}{c}Simplification Rules\end{tabular}}
+\frametitle{Simplification Rules}
 
 \begin{center}
 \bl{\begin{tabular}{rcl}