Researchers decide to set up a study to see if there is an association between drinking water from the wells on the school property before getting a gastrointestinal illness in November 1972. All 362 people agreed to participate. None experienced gastrointestinal illness before November. 251 drank water either at the school or in the apartment that used the same well water in November. Of those, 192 later developed gastrointestinal illness. 21 People who claimed they did not have any of the water also got sick. What is the relative risk