y - done
n - not done
(n)	Open an account
(y) Close an account; close restricted to zero balance accounts.
(y)	Deposit and withdraw money from an account.
(y)	Give warning messages for not sufficient funds (e.g., when
withdrawing).
(y)	Transfer a sum from one account to another.
(y)	Obtain account balances.
(y)	Give a warning message to the client if the balance on his/her
“chequing” account will drop down below the threshold of $1,000 – prior
to him/her executing the operation. If s/he decides to go ahead despite
the warning message, a charge of $2.00 is levied on the client for each
such transaction.
(n)	A client can open either savings or chequing account, or both; s/he
can add the complementary account at anytime.
(y)	The bank manager can display the account details of any given
customer, or all customers, and obtain aggregate data on the funds in
the bank, etc., categorised appropriately.

(n) There is also a role of a systems maintenance person who also has an
id to access the system. S/he can turn ON/OFF execution trace. If the
trace is ON, then the system will dump the execution traces in a file