Revenue per employee per product group

You're analyzing revenue for Company XYZ and want to understand what the revenue per employee was in 2017. You have the following tables:

Table: employees

Column Name	Data Type	Description
employeeid	integer	id of the employee
product_area	string	product area that employee works in
compensation	integer	yearly salary for employee

Table: revenue

Column Name	Data Type	Description
date	string	format is "YYYY-MM-DD
product_area	string	product area that employee works in
revenue	integer	revenue made on the given date in USD

Given the above, write a SQL query to calculate revenue per employee by product area.