CASE STUDY PROGRESS P.B. comes back in a week and tells you that she can get a low-cost oral contraceptive through a local store. You convey this information to the nurse practitioner, who examines P.B. and writes a prescription for a biphasic pill containing ethinyl estradiol and norethindrone. You are asked to discuss the use of the pill with P.B. 11. What key factors should you address with PB.?