A cohort study on the effectiveness of a treatment for alcoholism will follow 50 people for two years. In this time, it is expected that the number of people who drop out of the study due to relapse will be ten, with standard deviation four. It is also expected that the number of people who drop out of the study because they move out of the study area will be six, with a standard deviation of three. What is the SD of the number of people who will drop out due to either relapse or moving away? g