Laravel Eloquent groupby and sum

I'm really new to eloquent, and I'm trying groupby the employee_id and do a sum function on the deductions field.. but I'm really having a hard time trying to sum the deductions.

here's my code:

$payroll = Timelog::groupBy('employee_id')->with('employee')->get(['employee_id','deductions']);

what I did is to add sum function after the groupby but I'm having an error..

any help will be appreciated.

via Chebli Mohamed