SML

Problem 6 (20 points) The powerset of a set S is defined as the set of all subsets of S (including the empty set). For example, the powerset of {1, 2} is {{1, 2}, {1}, {2}, {}}. Write an SML function called powerset: 0a list ?0 a list list that when given a list representation of a set as input returns its powerset as output.