Suppose that thwo systems are connected in cascade

The two systems are specified as follows

S$1$: $1[]=1[]1[1]$

S$2$: $2[]=2[1]+2[2]$

$($a$)$ Determine the imoulse response of S$1$ and S$2.$

$($b$)$ Determine the frequency response of S$1$ and S$2.$

$($c$)$ Determine the frequency response of the overall system.

$($d$)$ Write one difference equation that defines the overall system in terms of $[]$ and $[]$ only