20. You will now sort the data according to Job Description first, then by City Employed and finally by Gross Salary (show the largest Salary first). Use the Subtotal feature to calculate the Sum of the Gross Salary for each Job Description. Use the Subtotal feature again but this time you are to calculate the average Gross Salary for each City Employed. Make sure the first subtotals remain intact. 20. You will now sort the data according to Job Description first, then by City Employed and finally by Gross Salary (show the largest Salary first). Use the Subtotal feature to calculate the Sum of the Gross Salary for each Job Description. Use the Subtotal feature again but this time you are to calculate the average Gross Salary for each City Employed. Make sure the first subtotals remain intact