Question 2 Programming by Contract (a) Design a BankAccount class for maintaining bank balances. Each bank account should have a current balance and methods implementing deposits and withdrawals; however money can only be withdrawn from an account if there are sufficient funds. Each account has a cash withdrawal limit of $800 per day Give Java implementations of the methods in your design. Explain how your implementation enforces the daily limit on withdrawals (b) Give preconditions and postconditions for each method in the BankAccount class and provide a rigorous argument that balan 2 0 is a class invariant. Explain how your code is consistent with your pre- and postconditions