Consider two causal linear time invariant systems with $H_1(z)=\frac{2}{1-a{z}^{-1}}$ and $H_2(z)=\frac{2}{1-b{z}^{-1}}$ where $a=7$ and $b=7.$ If $H(z)$ represents the parallel combination of the two systems, what is $h[1]?$

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