Dear emacs and org-mode comrades.

Given:

• a table with
  • a list of tags +
  • their number of appearances in question 1 (Q1) & and question 2 (Q2).
• org support for tag groups (https://orgmode.org/manual/Tag-Hierarchy.html)
• 3 defined tag groups
  • GroupTag1 (GT1)=tagA+tagC+tagD and
  • GroupTag2 (GT2)=tagB+tagE
  • GroupTag3 (GT3)=tagB+tagC+tagD (yes, some tags are in more than 1 group)

How can I count with pure elisp (assuming some table formula but I’m open to other ways) the sum of individual tag appearances of each tag group, for each question?

Example:

| tag  | Q1 | Q2 |
|------+----+----|
| tagA |  9 |    |
| tagB |  4 |  2 |
| tagC |  1 |  4 |
| tagD |    |  5 |
| tagE |    |  6 |
|------+----+----|
| GT1  | 10 |  9 |
| GT2  |  4 |  9 |
| GT3  |  5 | 11 |

Thanks a lot for your time and attention… :)