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 WorksFor respectively.

a)Find the names of people who work in both NYC and Boston.

b)Find the names of unemployed people who live in NYC.