Problem 1: Write a regular expression that recognizes the following language over the alphabet {a,b}: Any string containing the letters a and b, where the number of letters is not a multiple of three....

Extracted text: Problem 1: Write a regular expression that recognizes the following language over the alphabet {a,b}: Any string containing the letters a and b, where the number of letters is not a multiple of three. (Note that 0 is a multiple of three.) Your regular expression should contain only a and b, and the metacharacters (, ), *, +, ? and |. Problem 2: Write a context free grammar that recognizes language from Problem 1. Your start symbol should be named S.