In a double-entry accounting system, every business transaction has to be entered as two separate transactions, in different two accounts, once as a debit and once as a credit. For example,

if a business borrows $10,000 from a bank, the business should enter a debit of $10,000 to its Cash account and a credit of $10,000 to its notes Payable account. In order to be in balance, every debit in such a system must have a matching credit. Describe an efficient algorithm to test if a double-entry accounting system is in balance. What is the running time of your method in terms of n, the number of business transactions?