Table: canterbury_ratings
Columns: episode
air_date
timeslot
rating
share
18_49_rating_share
viewers_m
rank_timeslot
rank_night
rank_overall

Question: What's the average of shows that had a timeslot rank greater that 3 but still had a smaller viewership less than 4.87?
SQL: SELECT AVG("share") FROM canterbury_ratings WHERE "rank_timeslot" > 3 AND "viewers_m" < 4.87