Pay sales tax with the Retail Sales Tax Return For Occasional Sales (DR 0100A) on the tangible personal property included in the purchase of the business by the 20th day of the month following the sale.
So, to avoid pregnancy she has to better avoid unprotected sexual intercourse in this period. The rest of the days i.e., starting from menstruation to the 10th day and again from 21st day up to menstruation are the safe days or the safe period to avoid pregnancy.
Now you know your safe and unsafe period, but there is still one major challenge, which is discipline and commitiment of keeping your eye on the calender. The discipline aspect has to do with the willingness of the woman to abstain from Sex for one week each month according to the woman's menstrual calendar.