DIAN (Digital ANalog), a programming system developed by Farris (4), was used for solving the equations in the model. DIAN allows a digital computer to be programmed using analog computer programming techniques. The DIAN program deck is fed into the digital computer to instruct it to simulate an analog computer. Problem "patching" is simulated by means of a coded data deck. One IBM card represents each component of the simulated analog computer. A complete description of DIAN cannot be given here. Readers interested in using the system are referred to a programming guide by Farris and Burkhart (5). Since DIAN solves equations incrementally, the equations must be written in slightly different form than for programming on an analog computer. This is because of the particular incremental form of the inputs and outputs to the DIAN components illustrated in Figs. 7 and 8.