Database schema. Consider the following schema:

Customer : ID, Name, City

(where ID is the primary key.)

Account : Number, Branch, CustID, Balance

(where Number is the primary key and CustID is a foreign key referencing Customer on ID.)

Problem 1. Write the following queries in relational algebra:

(1) ID and name of customers who own an account in a branch in their city.

(2) ID and name of customers who do not own any account.

(3) ID and name of customers who own an account in every branch.

(4) ID and name of customers who own an account with a balance which is no less than the balance of any other account.