20.2 Disease D occurs in 25 percent of all the cases. Symptom S is observed in 75 percent of the patients suffering from disease D, and only in one sixth of other cases. Suppose we are building a decision tree for diagnosing disease D, so the classes are just D (person has D) and ~D (does not have D). S is one of the attributes. What are the information gain and gain ratio of attribute S?