In the circuit shown, $V_o = 3 V.$ Find $I_s$ given that $R_1 = 8 k\Omega, R_2 = 4 k\Omega, R_3 = 10 k\Omega, R_4 = 12 k\Omega, R_5 = 7 k\Omega$ and $R_6 = 4 k\Omega$.

$I_s =$ $mA$