The correct option is A Both A and R are true, and R is the correct explanation of A.
People make deposits in banks to safeguard their money. Banks use the deposited money to lend loans for various purposes. The banks, in turn, pay their customers with interest money. However, the interest rate/money on loans that banks lend to external sources is higher than the interest rate/money they pay their customers. The difference is the margin/profit banks make to run their businesses.