And we'll assume that the top of the ladder kind of glides along the side of the wall. It stays kind of in contact with the wall and moves straight down. And we see right over here, the arrow is moving straight down. And our question is, how fast is it moving straight down at that moment? So let's think about this a little bit. What do we know and what do we not know? So if we call the distance between the base of the wall and the base of the ladder, let's call that x.