A college student is a member of a sorority and has to pay monthly dues to the sorority for her residence. The sorority emailed out invoices on the first of the month, with payment due by the tenth. A parent who received an invoice put a check in the mail the day the email arrived, but the sorority says that the payment was not received until the eleventh and thus has charged a late fee. The bill says that if you pay by mail you should allow for five to seven days for the mail to arrive, which is less than the nine days that were left before payment was due. Can they charge a late fee when the check was sent as soon as the bill arrived, and when they accept payment by mail?

