354287.fig.002a
(a)
354287.fig.002b
(b)
354287.fig.002c
(c)
354287.fig.002d
(d)
Figure 2: Numerical simulation of (45) with ; hence is globally stable. Graphs (a) and (b) illustrate that and will eventually towards to steady state. Graphs (c) and (d) illustrate that , and will eventually towards to steady state. Initial values are , and .