The following causal IIR digital transfer functions were designed using the bilinear transformation

method with T $=0$:$5.$ Determine their respective parent causal analog transfer functions.

$($a$)$ Ga$($z$)=$

$4($z$2+3$z $+4)$

$10$z$2+4$z $+6$

$($b$)$ Gb$($z$)=$

$54$z$3+62$z$2+26$z $+18$

$(3$z $+1)(12$z$24$z $+8)$