What's the average of shows that had a timeslot rank greater that 3 but still had a smaller viewership less than 4.87?
CREATE TABLE "weekly_ratings" (
  "episode" text,
  "air_date" text,
  "timeslot" text,
  "rating" real,
  "share" real,
  "18_49_rating_share" text,
  "viewers_m" real,
  "rank_timeslot" real,
  "rank_night" real,
  "rank_overall" real
);
SELECT AVG("share") FROM "weekly_ratings" WHERE "rank_timeslot">3 AND "viewers_m"<4.87;