Shallow copy и Account

Что выведет изменение Account в person1?

<?php
class Account { public function __construct(public float $balance) {} }
class Person { public function __construct(public Account $account) {} }
$person1 = new Person(new Account(100));
$person2 = clone $person1;
$person1->account->balance += 50;
echo $person2->account->balance;