(4 days ago) What!?
85 is the best I could do, in nearly an hour. :O
EDIT 2023, 4th July: I had several 85s, untill today. Then I found a 79, and after that quite fast got it down to 73. This was definitely one of the hardest PhD levels, for me, untill now.
Wooow, soooo tricky!
At first I was very far, then I saw the other way and came 2 off. After that it still took me quite many tries, to do it right, for 66. Very good!
Insights