Please answer both questions and show work.18. A stock had returns of 11%, -18%, -21%, 20%, and 34% over the past 5 years. What is the standard deviation of these returns?19. The commons stock of Air United inc. had annual returns of 15.6%, 2.4%, -11.8%, and 32.9% over the last 4 years respectively. What is the standard deviation of these returns?