Among professors with the highest teachability, how many of their students have high salary?
highest teachability refers to MAX(teachability); high salary refers to salary = 'high';
SELECT COUNT(T1.student_id) FROM RA AS T1 INNER JOIN prof AS T2 ON T1.prof_id = T2.prof_id WHERE T1.salary = 'high' ORDER BY T2.teachingability DESC LIMIT 1