For each predator-prey system, determine which of the variables, x or y, represents the prey population and which represents the predator population. Is the growth of the prey restricted just by the predators or by other factors as well? Do the predators feed only on the prey or do they have additional food sources? Explain.
(a) dx / dt = -0.05x + 0.0001xy
dy / dt = 0.1y - 0.005xy
(b) dx / dt = 0.2x - 0.0002x2 - 0.006xy
dy / dt = -0.015y + 0.00008xy