QUESTION 3 (10 MARKS)

In terms of the following relations: (primary key foreign key) employee (person_ID, person_name, street, city) works at (person_ID, company_ID, salary) company (company_ID, company_name, city) manages (person_ID, manager_person_ID)

Where an employee can work in many companies (i.e., works at). All employees have a manager; manager_person_ID is a foreign key that refers to employee.personID.

Give relational algebra (not SQL) expressions for each of the following: i. Names of employees managed by Bob Builder (2 marks) ii. Names of employees who work at the Company called Bobsleigh Co and at the Company called Warren Co (2 marks) iii. Names of employees who do not work for Bobsleigh Co (2 marks) iv. Names of any employees who work at all of the companies (4 marks)