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Two systems $H_l(z)$ and $H_2(z)$ are connected in cascade as shown below. The overall output y(n) is the same as the input $x(n)$ with a one unit delay. The transfer function of the second system $\mathrm{H}_2(z)$ is

1. $\frac{\left(1-0.6 z^{-1}\right)}{z^{-1}\left(1-0.4 z^{-1}\right)}$
2. $\frac{z^{-1}\left(1-0.6 z^{-1}\right)}{\left(1-0.4 z^{-1}\right)}$
3. $\frac{z^{-1}\left(1-0.4 z^{-1}\right)}{\left(1-0.6 z^{-1}\right)}$
4. $\frac{\left(1-0.4 z^{-1}\right)}{z^{-1}\left(1-0.6 z^{-1}\right)}$