$($a$)$ Taking the left part from points A and B as the Thevenin equivalent circuit, what is the value of VTH$?($unit: V$)$

$($b$)$ What is the value of RTH$?($unit: k$)$

$($c$)$ Taking the left part from points A and B as the Norton equivalent circuit, what is the value of IN$?($unit: V$)$

$($d$)$ Please use the voltage$/$current source transform formula to verify your answer of $($a$)$ and $($c$)$ are both correct.