What is the correlation between the review starts and business stars?
highest review count refers to review_count = 'Uber'; average business review stars = Divide (Sum(review_stars), Count(user_id))
SELECT CAST(SUM(T2.review_stars) AS REAL) / COUNT(T1.business_id) FROM Business AS T1 INNER JOIN Reviews AS T2 ON T1.business_id = T2.business_id