Argument 1 passed to App\Notifications\NewInstalasi::__construct() must be an instance of App\Models\User, instance of App\Models\Instalasi given

i am doing project with notification real time use pusher in laravel 8, and then i have got this error "Argument 1 passed to App\Notifications\NewInstalasi::__construct() must be an instance of App\Models\User, instance of App\Models\Instalasi given, called in C:\xampp\htdocs\rsud\laporan_teknisi_improvement\app\Observers\InstalasiObserver.php on line 15".

in my Notification/NewInstalasi.php codes :

<?php

namespace App\Notifications;

use Illuminate\Bus\Queueable;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Notifications\Messages\MailMessage;
use Illuminate\Notifications\Notification;
use App\Models\User;
use App\Models\Instalasi;

class NewInstalasi extends Notification implements ShouldQueue
{
    use Queueable;

    /**
     * Create a new notification instance.
     *
     * @return void
     */

     protected $user, $instalasi;
    public function __construct(User $users, Instalasi $instalasi)
    {
        $this->instalasi = $instalasi;
        $this->users = $users;
    }

    /**
     * Get the notification's delivery channels.
     *
     * @param  mixed  $notifiable
     * @return array
     */
    public function via($notifiable)
    {
        return ['database', 'broadcast'];
    }

    /**
     * Get the mail representation of the notification.
     *
     * @param  mixed  $notifiable
     * @return \Illuminate\Notifications\Messages\MailMessage
     */
    public function toMail($notifiable)
    {
        return (new MailMessage)
                    ->line('The introduction to the notification.')
                    ->action('Notification Action', url('/'))
                    ->line('Thank you for using our application!');
    }

    /**
     * Get the array representation of the notification.
     *
     * @param  mixed  $notifiable
     * @return array
     */
    public function toArray($notifiable)
    {
        return [
            'user_id' => $this->users->id,
            'user_name' => $this->users->name,
            'instalasi' => $this->instalasi->nama,
        ];
    }
}

and in Observer/InstalasiObserver.php codes :

<?php
namespace App\Observers;

use App\Notifications\NewInstalasi;
use App\Models\User;
use App\Models\Instalasi;

class InstalasiObserver
{
    public function created(Instalasi $instalasi)
    {
        $author = $instalasi->user;
        $users = User::all();
        foreach ($users as $user) {
            $user->notify(new NewInstalasi($instalasi,$author));
        }
    }
}