Use formula in agenda clockreport to convert time? (pomodoro count in Agenda)

Question

I'm trying to make the Agenda Clockreport show how many pomodoros I've invested in a task. A Pomodoro is 25 minutes. For example, 1:15 hours of work is 3 pomodoros.

I'm trying to customize org-agenda-clockreport-paramater-plist, and I would like to extract "Time" and convert it to a pomodoro. I.e., (time in minutes / 25) = pomodoro.

I was considering using :formula from The Clock Table but I'm not sure where to begin or where to look for examples.

Is this technically possible somehow?

[edit Solution]
Thanks to Sacha's post, I use the config as following:

(setq org-agenda-clockreport-parameter-plist 
 '(:fileskip0 t :link t :maxlevel 2 :formula "$5=($3+$4)*(60/25);t"))

This creates a report that skips empty org-agenda files, has 2 levels depth and adds a column that shows pomodoros with 2 decimals. ('t' = time in hours).

E.g screenshot:

If you like, please remember to up-vote Sacha's answer.

Answer 1

This will create a column in your clocktable report that sums the hours from columns 3 and 4, and then another column that shows you the round number of pomodoros that took up.

(setq org-agenda-clockreport-parameter-plist 
      '(:link t :maxlevel 2 :formula "$5=$3+$4;t::$6=ceil($5*60/25);N"))

If you don't want in-between columns, here's a totally hackish approach:

(defun my/org-minutes-to-clocksum-string (m)
  "Format number of minutes as a clocksum string.
Shows the number of 25-minute pomodoros."
  (format "%dp" (ceiling (/ m 25))))
(fset 'org-minutes-to-clocksum-string 'my/org-minutes-to-clocksum-string)

Alternatively, you can use :formatter, but the formatting function looks very long and annoying to change.

Hope this helps!