A system with the open loop transfer function $$G\left( s \right) = {K \over {s\left( {s + 2} \right)\left( {{s^2} + 2s + 2} \right)}}$$ is connected in a negative feedback configuration with a feedback gain of unity. For the closed loop system to be marginally stable, the value of $$K$$ is ________.

For the given system, it is desired that the system be stable. The minimum value of $$\alpha $$ for this condition is _________

The feedback system shown below oscillates at $$2$$ rad/s when

Figure shows a feedback system where $$K>0$$

The range of $$k$$ for which system is stable will by given by