diff --git a/app/Http/Controllers/ConcertOrdersController.php b/app/Http/Controllers/ConcertOrdersController.php
index 8309212..baa3452 100644
--- a/app/Http/Controllers/ConcertOrdersController.php
+++ b/app/Http/Controllers/ConcertOrdersController.php
@@ -4,6 +4,7 @@ namespace App\Http\Controllers;
 
 use App\Order;
 use App\Concert;
+use App\Reservation;
 use Illuminate\Http\Request;
 use App\Billing\PaymentGateway;
 use App\Billing\PaymentFailedException;
@@ -31,12 +32,13 @@ class ConcertOrdersController extends Controller
         try {
             // Find some tickets
             $tickets = $concert->findTickets(request('ticket_quantity'));
+            $reservation = new Reservation($tickets);
 
             // Charge the customer for the tickets
-            $this->paymentGateway->charge($tickets->sum('price'), request('payment_token'));
+            $this->paymentGateway->charge($reservation->totalCost(), request('payment_token'));
 
             // Create an order for those tickets
-            $order = Order::forTickets($tickets, request('email'), $tickets->sum('price'));
+            $order = Order::forTickets($tickets, request('email'), $reservation->totalCost());
 
             return response()->json($order, 201);
 
diff --git a/app/Reservation.php b/app/Reservation.php
new file mode 100644
index 0000000..2993db9
--- /dev/null
+++ b/app/Reservation.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace App;
+
+class Reservation
+{
+    private $tickets;
+
+    public function __construct($tickets)
+    {
+        $this->tickets = $tickets;
+    }
+
+    public function totalCost()
+    {
+        return $this->tickets->sum('price');
+    }
+}
diff --git a/tests/unit/ReservationTest.php b/tests/unit/ReservationTest.php
new file mode 100644
index 0000000..34ab327
--- /dev/null
+++ b/tests/unit/ReservationTest.php
@@ -0,0 +1,23 @@
+<?php
+
+use App\Concert;
+use App\Reservation;
+use Illuminate\Foundation\Testing\WithoutMiddleware;
+use Illuminate\Foundation\Testing\DatabaseMigrations;
+use Illuminate\Foundation\Testing\DatabaseTransactions;
+
+class ReservationTest extends TestCase
+{
+    use DatabaseMigrations;
+
+    /** @test */
+    function calculating_the_total_cost()
+    {
+        $concert = factory(Concert::class)->create(['ticket_price' => 1200])->addTickets(3);
+        $tickets = $concert->findTickets(3);
+
+        $reservation = new Reservation($tickets);
+
+        $this->assertEquals(3600, $reservation->totalCost());
+    }
+}