A simple threecompartment model that describes nutrients in a food chain has been studied by M. R. Cullen.1 (See Fig. 6.2. 16.) For example, the constant a31 = 0.04 alongside the arrow connecting compartment I (phytoplankton) to compartment 3 (zooplankton) means that at any given time, nutrients pass from the phytoplankton compartment to the zooplankton compartment at the rate of 0.04x1 per hour. Find the linear system = A that describes the amount of nutrients in each compartment.