Given a list a containing multiple positive integers. Count how many ways there are such that the selected subset is exactly equal to k. For example: set {1,2,3} : if k=3, then output 2 because the sum of {1,2},{3} is 3 . If k=5,1 should be output because the sum of {2,3} is 5 . If k=7,0 should be output. Input: The input is two lists a, b. a is the set to be evaluated. ( len (a)