Since this is a checking account, you are required to enforce an invariant that the balance is never negative.

Since this is a checking account, you are required to enforce an invariant that the balance is never negative.With this invariant in mind,

a) (5pt) Explain why the given code is a bad design for the abstract data type BankAccount.

b) (15pt) Write down a better implementation for BankAccount in Java (or your favorite OO language).