Stability & error from nyquist POLAR plot?
Hints: -


What is the open loop gain at DC (frequency = 0 Hz)?
What is the closed loop DC gain after applying unity gain negative feedback?
Can you tell the system will be stable when the loop is closed? If you can, what will the phase margin be approximately?
What is the gain margin?
Do you understand how these margins work in a bode plot?


After further questions about bode versus Nyquist I'm showing a simple equivalence: -



Can you see how the phase margin is seen on the Nyquist plot compared to how it is seen (easier of course) on the Bode plot?

Can you see that the unity gain circle in the Nyquist plot can predict the phase margin and gain margin?