See announcement from Marc (that ended up in discussion forum, perhaps some are not getting emails from there):
The second problem in Exercise 4 turned out to be more difficult than I initially expected — in fact, it cannot be solved in the way it is currently stated. I apologize for this!
We have therefore decided not to grade Exercise 4(2). It will not count toward the final points, but up to 2 extra points will be awarded for reasonable attempts to solve it.
I wish you all good luck on the exam!
Marc
/Anna