Extjs - how can I add subtotal/summary for each Grid Grouping row?

Question

Using an ExtJS 3.4 grid, how can I achieve the neat sub-total row under every Grouped section as in the following example:

http://dev.sencha.com/playpen/gxt/totals/

I'm unable to upgrade as 3.4 is the version used by the CMS I use (MODX).

Answer 1

Never mind, the same example is given for 3.4:

http://dev.sencha.com/deploy/ext-3.4.0/examples/grid/totals.html