Among the students with high salary, what is total number of students with a GPA higher than 3?
high salary refers to salary = 'high'; GPA higher than 3 refers to gpa > 3;
SELECT COUNT(T1.student_id) FROM RA AS T1 INNER JOIN student AS T2 ON T1.student_id = T2.student_id WHERE T1.salary = 'high' AND T2.gpa > 3