Suppose we have {6,2,1,3}. If k is a number so that the sum of k and any number in the set above is also in the set, what is the value of k?
S consists of a set of numbers from -50 to 50 (zero inclusive), we have to pick a set K such that K consists of {A, B, C} such that the sum of numbers in set K is equal to zero. How many such sets are possible?