3. (2.5+2.5pts) Consider the instructor relation shown below. a) Construct a bitmap index on the attribute salary, dividing salary values into four ranges: below 50,000,50,000 to below 60,000,60,000 to below 70,000 , and 70,000 and above b) Consider a query that requests all instructors in the Finance department with salary of 80,000 or more. Outline the steps in answering the query, and show the final and intermediate bitmaps constructed to answer the query