What is the average Elitestar rating for a Yelp_Business that closes at 12PM on Sundays?
average Elitestar rating refers to DIVIDE(SUM(stars), COUNT(business_id)); closes at 12PM refers to closing_time = '12PM'; on Sundays refers to day_of_week = 'Sunday'
SELECT CAST(SUM(T3.stars) AS REAL) / COUNT(T1.business_id) AS "average stars" FROM Business_Hours AS T1 INNER JOIN Days AS T2 ON T1.day_id = T2.day_id INNER JOIN Business AS T3 ON T1.business_id = T3.business_id WHERE T2.day_of_week LIKE 'Sunday' AND T1.closing_time LIKE '12PM'