\begin{frame}{Exercise}
  \begin{exampleblock}{}
    Construct an NFA that accepts the language generated by 
    \begin{talign}
      S &\to aT & T &\to abcS \mid b
    \end{talign}
  \end{exampleblock}
  \bigskip

  Note that $T \to abS \mid b$ is short for two rules:
  \begin{talign}
    T &\to abcS\\
    T &\to b
  \end{talign}
\end{frame}