Consider the following system of equations:

\(Y_{1}=\alpha_{0}+\alpha_{1} Y_{2}+\alpha_{3} Y_{3}+\alpha_{4} X_{1}+\alpha_{5} X_{2}+U_{1}\)

\(Y_{2}=\beta_{0}+\beta_{1} Y_{3}+\beta_{2} Y_{1}+\beta_{3} X_{2}+U_{2}\)

\(\mathrm{Y}_{3}=\lambda_{0}+\lambda_{1} \mathrm{x}_{1}+\lambda_{2} \mathrm{x}_{2}+\lambda_{3} \mathrm{x}_{3}+\mathrm{U}_{3}\)

According to the order condition, the first equation is: