Irene has a credit card that uses the previous balance method. The opening

balance of one of her 30-day billing cycles was $2510, but that was her

balance for only the first 5 days of the billing cycle, because she then paid off

her entire balance and didn't make any new purchases. If her credit card's

APR is 11%, which of these expressions could be used to calculate the

amount Irene was charged in interest for the billing cycle?