$4.$ Find the zero$-$state response $($convolution$)$ of the system: h$[$n$]=(0\mathrm{.}5)$nu$[$n$]$ If the input is: $($a$)$ x$[$n$]=2$nu$[$n$]($b$)2$nu$[$n$]($Hint: use the following formula$)$ Xn k$=0$ kxk $=$ x $($n $+1)$x n$+1+$ nxn$+2(1$ x$)2$