l5. How many distinct permutations are there of the letters in \"perfect"? 1'. How many distinct permutations are there of the digits in 1121231234? 3. For n a 5. consider strings of length 11 using elements of {a.b.c.d.e}. Assume all such strings are equally likely. a. What is the probability that a string selected at random has exactly three a's? b. What is the probability that such a string has exactly two b's given that it has exactly three a's? 9. How many distinct permutations are there of the letters in \"breeze"? 1U. Three pollsters canvas 21 houses. Each pollster will visit seven houses. How many different assignments of pollsters to houses are possible