Please list the full names of all the students who are research assistants with the highest research capability.
research assistant refers to the student who serves for research where the abbreviation is RA; the highest research capability refers to capability = 5; full name refers to f_name and l_name;
SELECT T1.f_name, T1.l_name FROM student AS T1 INNER JOIN RA AS T2 ON T1.student_id = T2.student_id WHERE T2.capability = 5