As Sarah is 70 years old and has Medicare benefits, she may not need to purchase health care insurance under the Affordable Care Act. Medicare is a federal health insurance program for people who are 65 years or older, as well as for younger people with certain disabilities or illnesses. It provides coverage for a wide range of health care services, including hospital stays, doctor visits, and prescription drugs. Therefore, Sarah may already have the necessary health insurance coverage, and may not need to purchase additional insurance under the Affordable Care Act. However, the specifics of Sarah's situation and her health care needs should be carefully evaluated to ensure that she has the best coverage for her needs.