$*4\mathrm{.}29.$ Consider the circuit shown in Fig. $4\mathrm{.}62,$ where $I_1$ is a $1-mA$ ideal current source and $I_S=3{10}^{-17}A.$

$($a$)$ Assuming $V_A=,$ determine $V_B$ such that $I_C=1mA.$

$($b$)$ If $V_A=5V,$ determine $V_B$ such that $I_C=1mA$ for a collector$-$emitter voltage of $1\mathrm{.}5$ V $.$