, any spiking time $T\in[T^M_{min},T^{I^*}_{min})$ for a given $M<\w/z_d$ can be achieved with the minimum-power control $I^*_0$ as given in , any $T\in[T^{I^*}_{min},T^{I^*}_{max}]$ can be achieved with minimum power by $I^*$ in , and moreover any $T\in(T^{I^*}_{max},T^M_{max}]$ can be obtained by switching between $I^*$ and $I^*_{max}$