Write SQL query to solve given problem: What is the average capability of students with less than a 2.5 GPA?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(SUM(T1.capability) AS REAL) / COUNT(T1.student_id) FROM RA AS T1 INNER JOIN student AS T2 ON T1.student_id = T2.student_id WHERE T2.gpa < 2.5