1. (10 points) Recall the following definitions (from page 44) on languages (sets of strings) A, B: Union AU B = {x | x A or x B} Concatenation Ao -{zy 1 TE A and y E B} Star Afrir2...lk kE Z and k 20 and each ri E A) For each of the following languages (sets of strings) over the alphabet (a,b), answer the following questions: (a) Is e (the empty string) in the set? (b) Classify each string over [a, b of length 2 as in the set or not in the set. Briefly justify each classification 2. fa) o fa, b, ab 3. w E ab, ba bb is not a substring of w 4. The language described by the regular expression a b*