Prob $1|$ For each open$-$loop transfer function given below, considering a unity negative feedback system, determine its closed$-$loop stability and the number of poles in the right half$-$plane $($unstable poles$).$ a$)(4$ points$)$ L$($s$)=2($s $+1)$ s $3+$ s $2+2$s $+1$ b$)(4$ points$)$ L$($s$)=4($s $+2)$ s$($s $3+2$s $2+3$s $+4)$ c$)(4$ points$)$ L$($s$)=2($s $+4)$ s $2($s $+1)$ d$)(4$ points$)$ L$($s$)=1$ s$(2$s $4+3$s $3+2$s $2+3$s $+2)$