Correct option is : (3) 10 mA
Voltage across \(800\ \Omega = 12 V - 4\ V\)
\( i = \frac{8}{800}10\ mA\)
i = i (current through Zener diode) + i (current through \(400\ \Omega \)resister)
\(10 \ mA = i_z+ \frac{4}{400} \Rightarrow 10\ mA = I_z + 10\ mA\)
\(I_z = 0\)
