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?
1) $2510 * (11/365) * 30
2) $2510 * (11/365) * 5
3) $2510 * (11/365) * 25
4) $2510 * (11/365) * 30 - $2510
