When integrating over a 2-dimensional region, students often set the
bounds as the rectangular hull.
(EG, the unit disc as $\int_{x=-1}^1 \int_{y=-1}^1$ !)

This is b/c they have no idea what the bounds mean.

If they -draw- regions and write the bounds, they won't make this
mistake.

The 2 ways to understand their mistake are:
- draw the damn region
- yes, x and y both range from $-1$ to $1$
  ...but not at the same time!
