I need the first question to be solved. (a) Show that the OLS estimator of ?1 obtained from model (1

I need the first question to be solved. (a) Show that the OLS estimator of ?1 obtained from model (1) is biased.(b) When is this bias equal to 0?(c) Derive the OLS estimators of ?1 and ?2 from model (2).(d) Show that, when the sample covariance between x1i and x2iis equal to 0, thenthe OLS estimator of ?1 derived in (c) is the same as the OLS estimator of ?1derived in (a).