-Consider the following table definition, where the primary keys are underlined. Give an expression in relational algebra for each of the following queries.

Athlete (aID integer, aName string, ranking integer, age integer)

Event (eID string, eName string, eLocation string)

Competes (aID integer, eID string, sport string, year integer)

6. Find the names of athletes who have competed in both XGames and Dew Tour

7. Find the aID of athletes over the age of 19 who have not competed in XGames

8. Find the names of any athletes who competed in all events