请教大家:

(1) Y = α + βX+ γZ  + U, where U is the error term with thedesired OLS properties,

If the variableX in (1) can be described by the equation:   

(3) X= δ0 + δ1Y+ δ2G +δ3T+W , where G and T are exogenous variables,and W is the error term, show whether or not the OLS estimate of β in (1) is unbiased.
谢谢.