Consider the following transfer function for a system with repeated poles at s $=$j

on the imaginary axis:

H$($s$)=1$

$($s$2+1)2$

Determine the output y$($t$)=$ h$($t$)$ x$($t$)$ of the system, given the input x$($t$)=$ u$($t$),$

where u$($t$)$ is the unit step function. Additionally, analyze the stability of the system

H$($s$)$: is it BIBO unstable? is it marginally stable?