a. Explain why regex commonly used in text editors are not regular expressions. [5 marks] b. Can the language {anbnn3} be accepted by a DFA? Justify your answer. [8 marks] c. Construct a context-free grammars for each of the given regular expressions. The alphabet is {a,b}. Indicate terminals and non-terminals. i. a ii. ab(abb)ba iii. (ba)(bbaa)+aaa(ab) [6 marks] d. Explain in which logical phase, or phases, of a compiler context-free grammars can be useful. [6 marks]