Given a int numList, for each non-empty subset of numList, compute the average of its elements, then return the average of those averages.
|-||The returned value must have an absolute or relative error less than 1e-9.|
numList will contain between 1 and 8 elements, inclusive.
All elements of numList will be between -1000 and 1000, inclusive.
All elements of numList will be distinct.