In each case, find a shortest word over the alphabet {A, B} that is not in the language of the regular expression: (i) A*B* [2 marks (ii) (A*IB*)(A*IB*)(A*|B*) [2 mark: (iii) A*(BAB)*A* [2 mark (c) In the programming language PASCAL, an identifier is an alpha- numeric sequence of characters beginning with a letter. [Note: a character is alpha-numeric if it is either a letter or a digit.] (i) Describe PASCAL identifiers via a regular expression. (ii) There is a finite list of so-called reserved words in PASCAL, such as WHILE and IF, which are not regarded as "proper" identifiers. So, a proper identifier is an identifier that is not on that list. Is the language of proper identifiers also a regular language, or is it not, or does this depend on the list? Justify your answer. [2 marks] [3 marks]