$4\mathrm{.}22.$ Determine the operating point and the small$-$signal model of $Q_1$ for each of the circuits shown in Fig. $4\mathrm{.}59.$ Assume $I_S=8{10}^{-16}A,=100,$ and $V_A=.$

$($a$)$

$($c$)$

$($d$)$

Figure $4\mathrm{.}59$