Express the following queries in Relational Calculus. A phone company has set up the following database in order to be able to send detailed bills to its customers:

CUSTOMER(Phone#,FirstName, LastName, City),

CALL(CallerPhone#, CalledPhone#, Date, Time, Duration, Cost),

The keys of the relations are underlined

Express the following queries in Relational Calculus:Explain each step

1. Print a detailed call log (CalledPhone#, Date, Time, Duration, cost) for John Stewart for the month of August 2021
2. Print a detailed call log (CalledPhone#, Date, Time, Duration, cost) for all the customers for the month of August 2021
3. Print the phone numbers John Stewart called between September 1st and September 15th, 2021
4. Print the name of the customers who called at least one number John Stewart called between September 1st and September 15th, 2021
5. Print the name of the customers living in the same city as John Stewart that John Smith has never called
6. Print the names of the customers who made at least one phone call on September 1^st, 2021
7. Print the names of the customers who did not make any phone call since September 1^st, 2021
8. On which days, all the customers made at least one call?
9. If we assume that customers call only people in their contact lists, print pairs of customers who have at least 1 common contact.