Sum data that needs to be joined and grouped by
You're right, I cannot simplify it anymore ;-)

Most reviews are about commenting bad code/habits and making suggestions how to improve it. But you're lucky, to me, there is nothing bad to say about your snippet so this will be a short review (and probably a reason why there are no anwers yet). 

You use clear names for the properties and variables where you use the first letter of the collection name or something derived (like type). You also use meaningfull names for the properties of the anonymous objects.

If the rest of your code looks as clean as this small sample you should be happy ;-)