1. Consider a database with the following schema: Person (name, age, gender) // name is a key Frequents (name, pizzeria) // [name, pizzeria) is a key Eats (name, pizza) // [name,pizza) is a key Serves (pizzeria, pizza, price) // (pizzeria, pizza) is a key Write relational algebra expressions for the following nine queries. (Warning: some of the later queries are a bit challenging.) a. Find all pizzerias frequented by at least one person under the age of 18. b. Find the names of all females who eat either mushroom or pepperoni pizza (or both). c. Find the names of all females who eat both mushroom and pepperoni pizza. d. Find all pizzerias that serve at least one pizza that Amy eats for less than $10.00. e. Find all pizzerias that are frequented by only females or only males. f. For each person, find all pizzas the person eats that are not served by any pizzeria the person frequents. Return all such person (name) / pizza pairs. g. Find the names of all people who frequent only pizzerias serving at least one pizza they eat. h. Find the names of all people who frequent every pizzeria serving at least one pizza they eat. i. Find the pizzeria serving the cheapest pepperoni pizza. In the case of ties, return all of the cheapest-pepperoni pizzerias