Using data from a tal distribution database, define a view named toplevelcust. it consists of the number, name, address, balance and credit limit of all customers with credit limits that are greater than or equal to $10,000. a. using sql, write the definition for toplevelcust. b. write an sql query to retrieve the number and name of all customers as well as the difference between their credit limit and balance in the toplevelcust view. c. convert the query you wrote in question 2b. to the query that the dbms will actually execute.