Sketch the Nyquist plot for each of the following specifications of G(z)H(z). and use th...

Sketch the Nyquist plot for each of the following specifications of G(z)H(z). and use the discrete-time Nyquist criterion to determine the range of values of K (if any such range exists) for which the closed-loop system is stable. [Note: In sketching the Nyquist plots, you may find it useful to first sketch the magnitude and phase plots as a function of frequency or at least calculate and at several points. Also, it is helpful to determine the values of ω for which is real.]