16. A & B

Find a regular expression for Give regular expressions for the following languages on sum = {a, b, c}. all strings containing exactly one a, all strings containing no more than three a's, all strings that contain at least one occurrence of each symbol in sum, all strings that contain no run of a's of length greater than two, all strings in which all runs of a's have lengths that are multiples of three. Write regular expressioas for the following languages on {0, 1}. all strings ending in 01, all strings not ending in 01, all strings containing an even number of 0's, all strings having at least two occurrences of the substring 00. (Note that with the usual interpretation of a substring, 000 contains two such occurrences), all strings with at most two occurrences of the substring 00, all strings not containing the substring 101