A bank has three types of accounts: checking, savings, and loan. Following are the attributes for each type of account:

CHECKING: Acct_No, Date_Opened, Balance, Service_Charge
SAVINGS: Acct_No, Date_Opened, Balance, Interest_Rate

LOAN: Acct_No, Date_Opened, Balance, Interest_Rate, Payment

Assume that each bank account must be a member of exactly one of these subtypes. At the end of each month, the bank computes the balance in each account and mails a statement to the customer holding that account. The balance computation depends on the type of the account. For example, a checking account balance may reflect a service charge, whereas a savings account balance may include an interest amount. Draw a class diagram to represent the situation. Your diagram should include an abstract class as well as an abstract operation for computing balance.