Consider the following earning regression model . EARNINGS= β₁+β₂S+β₃ EXP + μ a. Holding other factors constant, the OLS estimator β₃ is more accurate if b. there is less variation (lower mean square deviation) in the sample of EXP. c. S and EXP are more correlated. d. the variance of u is higher. e. there is more variation (higher mean square deviation) in the sample of S.