Cognos DMR Model Help

Here is a mock up chart what I'm supposed to create... I'm stuck as to how go about the total of my districts to display. The above chart is just a gist as to how my data looks
Untitled2.png

Earlier before posting this question, I used the exact expression like the one you have suggested... but it didn't work because I forgot to refer the lowest level data so used the descendants function.
Thank you so much for your prompt reply. :)