Solution:If, K - M = G - 1, the equation is exactly identified.
K-M>G - 1, The equation is over-identified.
K-M<G - 1, The equation is under-identified
In an equation, G = total no. of equations (total number of endogenous variables)
K = No. of total variables in the model.
M = No. of variables included in a particular equation.
Hence, for an exactly identified equation, the order condition that should be fulfilled is that equation must exclude one less than the total No. of endogenous variables in the model.