求解oracle习题.10.Write a query to display the department name,l

求解oracle习题.
10.Write a query to display the department name,location name,number of employees,and the average salary for all employees in that department.Label the columns’ dname,loc,Number of People,and Salary,respectively.
DNAME LOC Number of People Salary
------------ --------- ---------------- --------
ACCOUNTING NEW YORK 3 2916.67
RESEARCH DALLAS 5 2175
SALES CHICAGO 6 1566.67