. Use strong induction to show that every positive integer can be written as a sum of distinct powers of two, that is, as a sum of a subset of the integers 20 =1, 21 =2, 22 =4, and so on. [Hint: For the inductive step, separately consider the case where k+1 is even and where it is odd. When it is even, note that (k+1)∕2 is an integer.]