(8P.) Exercise 5 (Regular expression construction) Give a regular expression for the following languages over the alphabet = {a,b,c) Hint: figure out what are the shortest words in the language and check if they are covered by your regular expression. a) Li = {w E w begins with a or b and ends with abd) b) L2 = {w E * | w does not contain the infix ad) Hint: draw an automaton (NFA or DFA) for this language and obtain its regular expression as you have learned in the lecture. w has even length d) L4 = {w E . I to starts with a and contains the infix aba)