2. (30 points: 10 each) [Relational algebra] Textbook Exercise 8.23 a, b (extended), and c only. For the exercise b, extend the query condition to retrieve the serial_no and price of all cars that were sold at a price higher than $30,000 and had no option included. Note the exercise c is about a left outer join SALESPERSON IDASALE, not a natural join. In your relational algebra expressions, use equijoin for logical navigation (i.e., following a foreign key for join); apply selection condition as early as possible; and write the query in one relational algebra expression, not as a sequence of expressions using the rename operator