How much is the monthly fine of 5 yuan and 70 text messages?

5 yuan sends 70 short messages every month, with a penalty of three thousandths per day. The algorithm of late payment for the current month is three thousandths of the amount owed every day. The algorithm of late payment for next month is to deduct the contract package fee at the beginning of next month, add the amount owed before, multiply it by three thousandths and then multiply it by days.