Consider the following simultaneous equation model where Y1 and Y2 are endogenous variable while X1, X2, X3 and X4 are exogenous variables:
Y1t = α1 + α2Y2t + α3X1t + α4X2t + u1t (1)
Y2t = β1 + β2Y1t + β3X3t + β4X4t + u2t (2)
We can conclude that
a) Equation (1) is just identified while Equation (2) is over-identified
b) Both equations (1) and (2) are unidentified.
c) Equation (1) is unidentified while Equation (2) is just identified.
d) Both equations (1) and (2) are over-identified