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The impulse response $h[n]$ of a linear time-invariant system is given by

$h[n]=u[n+3]+u[n-2]-2 u[n-7]$

where $u[n]$ is the unit step sequence. The above system is

1. stable but not causal
2. stable and causal
3. causal but unstable
4. unstable and not causal