Consider the following relational database that stores information about credit card companies Issuer( bank, card) Bank_location(bank, location) Max Iimits( card, max limit An instance of the database is the following Issue Bank Amex Fist FederalVisa Fist FederaMasterCard Chase Citizens Citizens Citizens Fleet Card Bank_location Bank Amex Fist Federal Chase Citizens Fleet Am erican Express Visa Visa MasterCard Discoverv Visa Location Chicago LA NY Boston Boston Max_limits Card Visa MasterCard Discoverv American Express$500,000 Max limit $50,000 $100,000 $100,000 Write the following queries in relational algebra (note it is important to avoid "query by instance") 1. Which credit cards are issued by banks in Boston? 2. Which credit cards are not issued in NY? 3. Which banks issue credit cards with a limit less than $100,000? 4. Which banks issue only one credit card? 5. Which banks issue MasterCard and Visa but no other cards? 6. Which banks issue all credit cards