instance vs class attributes — and the bug ai ships every time

AI tried to update a class-level constant from inside an instance method. The intent was to change the rate for all Account instances. But self.rate = 0.05 doesn't update the class attribute — it creates a new instance attribute that shadows the class one, only on this instance.

Fix line 6 so it updates the class attribute directly. Use Account.rate = 0.05 instead of self.rate = 0.05.

Expected output (both accounts share the new rate):

0.05 0.05