Examine the identification of each of the three equations in the following simultaneous model : (括号内是脚标）

Y(1t) + b(12)Y（2t）＋　V(11)X(1t) = u(1t)

Y(2t) + V(21)X(1t) + V(22)X(2t) = u(2t)

Y(3t) + b(31)Y(1t) +b(32)Y(2t) + V(32)X(2t) = u(1t)