slight improvements to the files

Marius/uebung04/template.tex

@@ -25,6 +25,9 @@
 
 
 TODO:
+
+please define and describe your Cost function mathematically!
+
 \begin{itemize}
     \item change the tree, so that is is not trivial anymore with some more usage of \texttt{fill=red}
     \item add the costs (I would prefer relative costs from $s$ to $s'$, not the absolute paths costs), see the dummy value \textbf{C}