Fig. 2.

The trajectories of model (3) with $\mathit{\tau }=50$, $Y_c=45$, and a: $q=0.5$, $p=0.2$, $0.4$, $0.6$, and $0.8$, respectively; b $p=0.3$, $q=0.1$, $0.3$, $0.5$, and $0.7$, respectively