Consider the following relational schema (primary keys are underlined):

Person ( ssn, pn, age, city); a person's name and age, and the city he/she lives in Company ( cn, city); a companys name and the city it is located in

WorksFor ( ssn, cn, comp); the company a person works for and his/her compensation from this particular company (a person may work for several companies) Express the following queries in relational algebra.

You may use P,C, and W as shorthand for Person, Company , and Works For respectively.

c)

Some companies dont hire young people. Find the names of the companies that do not employ anyone younger than 25 years old.

d)

Some companies are really big ... Find the names of the companies that employ someone from every single city recorded in the Person table.