=+Depositors receive a 3.5% annual interest rate on their average deposit. AusBank earns an interest rate spread of 4% (the difference between the rate at which it lends money and the rate it pays depositors) by lending money at 7.5% (for simplicity sake we will ignore the lending differences between the customer segments). Account holders have unlimited use of services such as deposits, withdrawals, cheque accounts and foreign currency drafts. AusBank recently conducted an activity-based study of its services.