4. (a) Prove by simple induction that any postage amount of n cents, n > 48, may be achieved by using only 13-cent stamps and 5-cent stamps. That is, for every integer n > 48, there exist non-negative integers 4 and B such that, n = 134 + 5B. (b) Can your simple induction proof be applied to prove the above for all n 2 46? Obviously the base is correct since 46 = 13 x 2 + 5 x 4. Does your induction step still work? If not, explain why not