B$)$ Consider an echo removal system described by the difference equation $[]+[]=[](2)$ where y$[$n$]$ is the input and z$[$n$]$ is the output which has the echo removed. Show that Eq$.(2)$ is indeed an inverse of Eq$.(2\mathrm{.}21)$ by deriving the overall difference equation relating z$[$n$]$ to x$[$n$].$ Is z$[$n$]=$ x$[$n$]$ a valid solution to the overall difference equation?