At the close of Section 2.4.1, we suggest a model in which the CreditCard class supports a nonpublic method, set balance(b), that could be used by subclasses to affect a change to the balance, without...

class supports a nonpublic method, set balance(b), that could be used

by subclasses to affect a change to the balance, without directly accessing

the balance data member. Implement such a model, revising both the

CreditCard and PredatoryCreditCard classes accordingly.