List the case number of the crimes in wards with population below 52000 that have beat greater than the 90% of the average beat of all crimes.
population below 52000 refers to population < 52000; beat greater than the 90% of the average beat refers to beat > multiply(avg(beat), 0.9) where population < 52000
SELECT COUNT(T1.report_no) FROM Crime AS T1 INNER JOIN Ward AS T2 ON T1.ward_no = T2.ward_no WHERE T2.Population < 52000 AND T1.beat > ( SELECT AVG(T1.beat) * 0.9 FROM Crime AS T1 INNER JOIN Ward AS T2 ON T1.ward_no = T2.ward_no WHERE T2.Population < 52000 )