From the Herald. How did you get on? The answer is at the bottom of the article. I thought it was fairly easy (although I had to think about it for a few minutes) and definately an appropriate level for year 12 students.
http://www.nzherald.co.nz/lifestyle/news/article.cfm?c_id=6&objectid=11539869
What do you reckon - too hard for year 12 students?