due Jan 18 in class.

1. Problem 5 of ch 8 of parallel computing notes.

2. Show that any load 1 embedding of a complete binary tree on n nodes
   into an n node array must have dilation Omega(n/log n).

3. Problem 1 of notes on product graphs and hypercubes.

4. Problem 2 of notes on product graphs and hypercubes.