Payment Fees

A shop takes payments by card, by PayPal and in cash. Every payment has an amount, in cents, and a total: the amount plus a processing fee. The total is worked out the same way for every payment; only the fee depends on the kind of payment. That is what an abstract class is for: it holds the shared part, says that every payment has a fee, and leaves the fee itself to each kind of payment.

• The abstract class Payment is built from an amount, in cents, and keeps it. Its method fee() is abstract: every payment has a fee, but Payment can't say what it is. Its method total() is concrete: it returns the amount plus fee().
• Card, PayPal and Cash inherit from Payment, keep its total() as it is, and each writes its own fee():

• Card pays 2%: its fee is amount × 2 / 100.
• PayPal pays 3% plus 30 cents: its fee is amount × 3 / 100 + 30.
• Cash costs nothing: its fee is 0.

Swift has no abstract classes. As in the abstract-classes lesson, Payment's own fee() calls fatalError("must override"), and each subclass (: Payment) overrides it. The subclasses inherit init, amount and total. Dividing two Ints drops the fraction.

Every division rounds down: a card payment of 1999 cents has a fee of 39, not 39.98.

The starter code already has every class and every method header: declare the property and write the bodies. For each test, the harness creates the payments in the order given and prints two lines: each payment's total, total(), separated by spaces, and then the sum of all the fees. It calls them through the abstract type Payment, never through Card, PayPal or Cash.

Example 1:

Input:
    Card(1999)
    PayPal(500)
    Cash(700)
Output:
    2038 545 700
    84
Explanation: The card's fee is 1999 × 2 / 100 = 39 (39.98 rounded down), so its total is 2038. PayPal's fee is 500 × 3 / 100 + 30 = 45, total 545. Cash has no fee: total 700. The fees add up to 39 + 45 + 0 = 84.

Example 2:

Input:
    Card(49)
    PayPal(33)
    Card(50)
Output:
    49 63 51
    31
Explanation: 49 × 2 / 100 is 0.98, rounded down to 0. PayPal's 33 × 3 / 100 is 0.99, rounded down to 0, plus 30. The second card's 50 × 2 / 100 is exactly 1. The fees are 0 + 30 + 1 = 31.

Example 3:

Input:
    Card(0)
    PayPal(0)
    Cash(0)
Output:
    0 30 0
    30
Explanation: Amounts can be 0. PayPal still adds its 30 cents.

Constraints:

• Every test has between 1 and 100 payments.
• Every amount is an integer from 0 to 10⁶ cents.