What is the name of the cheapest product?
select product_name from products order by product_price asc limit 1
Show records where this product was complained about.
select * from complaints where product_id in (select product_id from products order by product_price asc limit 1)
Find the last name of the staff member who processed a complaint of this cheapest product.
select last_name from staff where staff_id in (select staff_id from complaints where product_id in (select product_id from products order by product_price asc limit 1))