I think you forgot to give the options along with this question. Based on my research and knowledge, i am answering the question and hope that the answer comes to your help. Zero correlation is the one that actually describes this situation correctly as "x" and "y" do not have any kind of relationship. I hope the answer comes to your help.
155.6 CM I divided 168 by 100 to find 1% then i got 1.68cm then I times that by 5 to find 5% which was 8.4cm. Finally I subtracted 168 and 8.4 to get 155.6 CM I hope that helped :)
Since the truck is 8 feet long then the longest log able to fit in the truck should be 8 feet as well. However talking reality, we might want to shorten it to make it fit better. Hope this helps!