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,...

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 directly accessing

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

CreditCard and PredatoryCreditCard classes accordingly.

Write a Python program that inputs a polynomial in standard algebraic

notation and outputs the first derivative of that polynomial.