find k numbers such that minimum difference of all the possible pairs of k numbers is maximum

Given an array of 'n' random integers. Find the k numbers such that the minimum difference of all the possible pairs of k numbers is maximum .

eg:Suppose the given elements are 11, 5, 6, 20, 30, 31, 60. then for k =4, answer should be 5 20 30 60 as minimum difference is maximum for this set.