Using the following relational schema for a COMPANY example, write down the relational algebra expressions for each of the following queries

1. Return the name of the projects that are in 'Houston'

2. Return the name of the departments that has a project in 'Houston'

3. The SSN of the employees who (a) do not have any dependents but (b) supervise an employee that works on a project in 'Houston'

EMPLOYEE Fname Minit Lname Ssn Bdate Address Sex Salary Super_ssn Dno DEPARTMENT Dname Dnumber Mgr_ssn Mgr_start_date DEPT_LOCATIONS Dnumber Dlocation PROJECT Pname Pnumber Plocation Dnum WORKS ON Essn Pno Hours DEPENDENT Essn Dependent_name Sex Bdate Relationship