"Information Gain" for a feature F is calculated as the difference between the entropy in the segment before the split (S1) and the partitions resulting from the split (S2). Where infogain = Entropy (S1) - Entropy (S2). So, need to figure out Entropy for both S1 and S2. Hope this helps. This is all I am working with here...hence, my being lost.

Compute the Information Gain for the following decision tree split