Sum collection variables

i have the next collection:

It is grouped by zone and fundo and I need to sum all the sup_ha that each fundo contains

      $transporFundo = $tansporCollect->groupBy(['zona','fundo']);
    
      foreach ($transporFundo as $fundo) {
        $supFundo = $fundo->sum('sup_ha');
        dd($supFundo);
      }

that is to say that for example of my collection for zona 1 and fundo 805 I would have to add the sup_ha field of the 364 records that are seen.

I tried to do it but I don't know how to access the field, as seen in my code I tried and it returns 0.

I hope you can help me, thanks

via Chebli Mohamed