The input-output relationship of a causal stable LTI system is given as $$y[n] = \alpha \: y[n-1] + \beta \: x[n]$$. If the impulse response $h[n]$ of this system satisfies the condition $\sum_{n=0}^{\infty}h[n]= 2$, the relationship between $\alpha$ and $\beta$ is
- $\alpha = 1-\beta /2$
- $\alpha = 1+\beta /2$
- $\alpha = 2\beta$
- $\alpha = -2\beta$