Hi,
This comes pretty late, but I say it anyway.
There was a minor mistake in the example solutions for week 4 Exercise 4.b. k_y was mistakenly labelled as k_z in a lot of places. Also I hinted the existence of certain intermediate steps which in reality were non-existing (There was a note “see (4) below” although there was no “(4)” to be found).
I updated the example solutions and these issues are now fixed.
-Lauri