Add Footer Row in Laravel Excel Export

Hello folks. I am now trying to export transactions for a duration with a header row (for column names), content rows (for each transaction), and a footer (to show the calculation of the total amount from each transaction price). I have done the first two, a header row and the transaction rows. But I am currently stuck with adding a footer row (to show the sum of the price of each transaction) at the end of the transaction rows. I have added the related codes below. Please check them and help me, folks. Thank you all in advance.

I think I may have to use the afterSheet method with RegistersEventListeners but do not know how to actually implement it.

TransactionsExport.php

<?php

namespace App\Exports;

use Carbon\Carbon;
use App\Models\Transaction;
use Maatwebsite\Excel\Events\AfterSheet;
use Maatwebsite\Excel\Concerns\FromQuery;
use Maatwebsite\Excel\Concerns\Exportable;
use Maatwebsite\Excel\Concerns\WithEvents;
use Maatwebsite\Excel\Concerns\WithStyles;
use Maatwebsite\Excel\Concerns\WithMapping;
use Maatwebsite\Excel\Concerns\WithHeadings;
use Maatwebsite\Excel\Concerns\ShouldAutoSize;
use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
use Maatwebsite\Excel\Concerns\RegistersEventListeners;
use Maatwebsite\Excel\Concerns\WithStrictNullComparison;

class TransactionsExport implements WithHeadings, WithMapping, ShouldAutoSize, FromQuery, WithStyles, WithStrictNullComparison, WithEvents
{
    use Exportable, RegistersEventListeners;

    public function __construct(int $days)
    {
        $this->days = $days;
    }

    public function styles(Worksheet $sheet)
    {
        return [
            // Style the first row as bold text.
            1    => ['font' => ['bold' => true]],
        ];
    }

    public function query()
    {
        return Transaction::query()
        ->with('customer', 'product')
        ->whereDate('created_at', '>=', Carbon::now()->subDays($this->days))
        ->orderBy('created_at', 'desc');
    }

    public function headings(): array
    {
        return [
            'Invoice No.',
            'Invoice Type',
            'Customer Name',
            'Product Name',
            'Total Price',
            'Paid Amount',
            'Balance',
        ];
    }

    /**
    * @var Transaction $transaction
    */
    public function map($transaction): array
    {
        return [
            $transaction->invoice_prefix . $transaction->invoice_no,
            $transaction->invoice_type,
            $transaction->customer->name,
            $transaction->product->name,
            $transaction->total_price,
            $transaction->payment_amount,
            $transaction->balance,
        ];
    }
}

ExportController.php

public function export(Request $request) {
        return (new TransactionsExport($request->days))->download('abc.xlsx');
}