The input-output transfer function of a plant $H(s)=\frac{100}{s(s+10)^2}$. The plant is placed in a unity negative feedback configuration as shown in the figure below.
The gain margin of the system under closed loop unity negative feedback is
- $0 \mathrm{~dB}$
- $20 \mathrm{~dB}$
- $26 \mathrm{~dB}$
- $46 \mathrm{~dB}$