Keith wrote:

> Also, the puzzles are missed numbered after puzzle 185.

Thanks, I've fixed that now.

> >*Puzzle 186*. Are the graphs we used above to describe the preorders A and B Hasse diagrams? Why or why not?

> No. A Hasse diagram must be acyclic, and the graph for A has a cycle.

Right!

Why must a Hasse diagram be acyclic, and why are we using a graph with a cycle here?