A task of analyzing database is given to the Database Administrator of the company having the following relational database and give an expression in relational algebra each of the following queries:

Employee (person-name, street, city)

Works (person name, company name, salary)

Company (Company name, city)

Managers (person name, manager-name)

Convert these relations into ER model and specify Primary Key, Foreign Key, Candidate Key and Super Key in these relations.