List wrangling question

I presume my question will be simple for some of you and I appreciate any input: I have 3 lists as shown on the screengrab below. I want to add elements of list 3 depending on the list 2 value to get a new list with 4 numbers (0+1, 2+3, 4+5+6, 7+8 in this example) Then I want to write this result in a new parameter of the rooms depending on the values of list 1. The concept is that you can identify all mass elements in a room get their total area and write it in a custom room parameter. Thanks !!

That’s what I was looking for

Thanks once again Vikram this works great