What is the popularity of the professor who advises the highest number of students with the highest research ability?
professor with the highest research ability refers to prof_id where MAX(capability);
SELECT T2.popularity FROM RA AS T1 INNER JOIN prof AS T2 ON T1.prof_id = T2.prof_id GROUP BY T1.prof_id, T1.capability ORDER BY COUNT(T1.student_id) DESC, T1.capability DESC LIMIT 1