employee (person_name, street, city) works (person_name, company_name, salary) company (company_name, city) manages(person_name, manager_name) Give an expression in relational algebra to express each of the following queries: Find the names of all employees who live in the city "Brooklyn". Find the names and cities of residence of all employees who earn a salary of at least $50,000. Find the names of all employees who work for the company "Fedco" and earn a salary of at least $50,000. Find the names and cities of residence of all employees who work for a company located in the city "Brooklyn". Find the names of employees who live in the city Brooklyn or in the city Hartford.