Which test levels would you use for these checkout failures?

In a fictional checkout, three defects were found: (A) a pure total-calculation function returns $22.00 for two $10.00 items with a 10% discount, although tax and shipping are both zero; (B) the order service sends the payment adapter an amount in dollars while the adapter contract expects integer cents; (C) a customer completes an approved sandbox payment, but the browser never displays the created order. Unit tests exercise isolated code, integration tests exercise collaborating components or boundaries, and system tests exercise the assembled application. No real payments may be made.