CREATE TABLE products (product_id VARCHAR(255), product_price VARCHAR(255)); CREATE TABLE complaints (staff_id VARCHAR(255), product_id VARCHAR(255)); CREATE TABLE staff (last_name VARCHAR(255), staff_id VARCHAR(255))
Find the last name of the staff member who processed the complaint of the cheapest product.
    
SQL: SELECT t1.last_name FROM staff AS t1 JOIN complaints AS t2 ON t1.staff_id = t2.staff_id JOIN products AS t3 ON t2.product_id = t3.product_id ORDER BY t3.product_price LIMIT 1