Write SQL query to solve given problem: How much higher is James Johnson's salary from the minimum salary of his title?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(REPLACE(SUBSTR(T1.salary, 4), ',', '') AS REAL) - CAST(REPLACE(SUBSTR(T2.minsalary, 4), ',', '') AS REAL) AS diff FROM employee AS T1  INNER JOIN position AS T2  ON T1.positionID = T2.positionID WHERE T1.lastname = 'Johnson' AND T1.firstname = 'James'