Differencing an equation in panel data analysis is useful to __________. Drawbacks however are that we __________ and __________. Please fill in the gaps choosing from the following possible options:Answer 1 eliminate part of the error term; decrease the sample size; decrease the variation in the regressor Answer 2 increase the sample size; add a part to the error term; decrease the variation in the regressor Answer 3 eliminate part of the error term; decrease the sample size; drop out the intercept Answer 4 increase the sample size; drop out the intercept; decrease the variation in the regressor