Calculate the average salary for employees who did inspection on License Re-Inspection.
inspection on License Re-Inspection refers to inspection_type = 'License Re-Inspection'; average salary = avg(salary)
SELECT AVG(T2.salary) FROM inspection AS T1 INNER JOIN employee AS T2 ON T1.employee_id = T2.employee_id WHERE T1.inspection_type = 'License Re-Inspection'