QUESTION 8 Which of the following constitutes a suitable simultaneous equations model (SEM)? y1 = B10 + 01>2 + B1121 + 41 Oa. >2 = P20 + 02y1 + 32122 + 12 where the variables z1 and z2 are exogenous y1 = 10 + 01>2 + B1121 + 41 Ob. )2 = P20 + 0zy1 + B2121 + 12 where the variable z1 is exogenous y1 = P10 + 01>2 + 1121 + 1272 + 41 Oc. Y2 = P20 + 02y1 + $2121 + 2272 + U2 where the variables z, and z2 are exogenous Od. All of the above