In article <Pine.NEB.firstname.lastname@example.org>, William Elliot <email@example.com> wrote:
> Consider an n by m grid of x's and o's. > > An x-path from the bottom squares of the grid to the top squares of the > grid considitues a seqence of horizontally or vertically adjacent > x-squares from some bottom x-square to some top x-square. Similar with > o-paths. > > An exit is a top square that is connected to a bottom square by > either an x-path or an o-path. For example, in the 8 by 3, x/o grid > > x x o o x x o o x > x o o x o x x x x > o o x x x o x o x > > has two o-exits and three x-exits for a total of five exits. > > In an n by m, x/o grid, what is the expected number of exits?