Among the professors who have more than 3 research assistants, how many of them are male?
research assistant refers to the student who serves for research where the abbreviation is RA; more than 3 research assistant refers to COUNT(student_id) > 3;
SELECT COUNT(*) FROM ( SELECT T2.prof_id FROM RA AS T1 INNER JOIN prof AS T2 ON T1.prof_id = T2.prof_id WHERE T2.gender = 'Male' GROUP BY T1.prof_id HAVING COUNT(T1.student_id) > 3 )