Table schema:
CREATE TABLE table_name_41 (evaluation_average__before_april_2009_ VARCHAR, _percentage_of_negative_evaluations VARCHAR, evaluation_average__from_april_2009_ VARCHAR)

Question: What is the mean Evaluation number (Before April 2009) when the percentage of negative evaluations was 0.8% and the mean Evaluation number of April 2009 was 4.2?
SQL: SELECT evaluation_average__before_april_2009_ FROM table_name_41 WHERE _percentage_of_negative_evaluations = "0.8%" AND evaluation_average__from_april_2009_ = "4.2"