These exercises introduce the issue of trying to decide how many hidden units are required (at minimum) to solve a problem of interest. We will focus on a small, but very challenging, problem: 5-bit parity. We will also examine how a change in decision about the architecture (i.e., the use of integration devices or of value units) can impact on the number of hidden units required, because of the different ways in which these two types of units carve up a pattern space into decision regions.