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?
CREATE TABLE "belt_requirements" (
  "evaluation_average_from_february_2011" real,
  "evaluation_average_from_april_2009" text,
  "evaluation_average_before_april_2009" text,
  "pct_of_negative_evaluations" text,
  "submitting_schedule_on_time" text,
  "punctuality_attendance_issues" text,
  "peak_lessons_taught" real
);
SELECT "evaluation_average_before_april_2009" FROM "belt_requirements" WHERE "pct_of_negative_evaluations"='0.8%' AND "evaluation_average_from_april_2009"='4.2';