Figure 1

The asymptotical stability of \((r_{2}^{*}, p_{2}^{*}, u_{2}^{*})=(2.8968, 0, 1.875)\). The parameters of system (5) are \(c_{1}=0.8\), \(c_{2}=0.1\), \(c_{3}=0.9\), \(c_{4}=0.6\), \(s_{1}=0.6\), \(s_{2}=0.1\), \(b=1.1\), \(d_{1}=0.9\), \(d_{2}=0.1\), \(d_{3}=0.1\), \(\alpha= 0.98\), and \(\tau=13.5\); the initial values are \(r(t)=0.1\), \(p(t)=1\), \(u(t)=2\) (\(t \in[-\tau,0]\))