Toby and Sarah both recently purchased health insurance with a 20% co-insurance rate, which means they pay 20% of the price of a doctor visit. Toby’s demand for doctor visits is QT = 6, and Sarah’s demand for doctor visits is QS = 20 – 0.10P, where Q represents the number visits and P is price per visit. With a price of $100 for doctor visits and a 20% co-insurance rate, how much out-of-pocket cost will Sarah pay per visit?