laravel eloquent sum of multiplied columns

1$amount = Transaction::sum(\DB::raw('jumla * harga'));
2

1$amount = Transaction::select(DB::raw('sum(jumlah * harga) as total'))->get();
2

1$amount = Transaction::all()->sum(function($t){ 
2    return $t->jumlah * $t->harga; 
3});
4