You are asked to design a software package for an On-line Banking System (OBS).

You are asked to design a software package for an On-line Banking System (OBS). The OBS will take requests from its user on the Internet. The requests include open an account with savings, checking, and CDs. Transfers between savings and checking, and Establish a CD are also among the requests. Close an account, or just close the savings account, withdraw CD are also permissible. Deposit, withdraw from a checking account are as routine requests.