CREATE TABLE "season_4_1999_2000" (
  "series_num" real,
  "season_num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text
);

Question: Which Directed by has an Original air date of april 29, 2000?
SQL: SELECT "directed_by" FROM "season_4_1999_2000" WHERE "original_air_date"='april 29, 2000';