What is the risk level of the establishment that Bob Benson inspected?
SELECT DISTINCT T3.risk_level FROM employee AS T1 INNER JOIN inspection AS T2 ON T1.employee_id = T2.employee_id INNER JOIN establishment AS T3 ON T2.license_no = T3.license_no WHERE T1.first_name = 'Bob' AND T1.last_name = 'Benson'