Consider the system described by following state space equations

$\begin{vmatrix} \dot{x_1}\\ \dot{x_2} \end{vmatrix}=\begin{vmatrix} 0 &1 \\ -1 & -1 \end{vmatrix}\begin{vmatrix} x_1\\x_2 \end{vmatrix}+\begin{vmatrix} 0\\1 \end{vmatrix}u$ ; $y=\begin{vmatrix} 1 & 0 \end{vmatrix}\begin{vmatrix} x_1\\ x_2 \end{vmatrix}$

If $u$ is unit step input, then the steady state error of the system is

1. $0$
2. $1/2$
3. $2/3$
4. $1$

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