CREATE TABLE Addresses (city VARCHAR, address_id VARCHAR)
CREATE TABLE Student_Addresses (address_id VARCHAR)

Find the id and city of the student address with the highest average monthly rental.
SELECT T2.address_id, T1.city FROM Addresses AS T1 JOIN Student_Addresses AS T2 ON T1.address_id = T2.address_id GROUP BY T2.address_id ORDER BY AVG(monthly_rental) DESC LIMIT 1
SELECT "T2"."address_id", "T1"."city" FROM "Addresses" AS "T1" JOIN "Student_Addresses" AS "T2" ON "T1"."address_id" = "T2"."address_id" GROUP BY "T2"."address_id" ORDER BY AVG("monthly_rental") DESC NULLS LAST LIMIT 1