THE CHALLENGE Consider the following grammar: 1. State in your own words what kinds of sentences (strings) these productions describe. (5 points) 2. Give 3 examples of valid strings, and 3 examples of invalid strings, according to the grammar. (5 points) 3. 3. Write a lexical analyzer (scanner) program for this BNF. (20 points) This scanner should prompt the user to input a string, then output a list of tokens and lexemes, one per line, from the input string according to the above grammar. If something is "wrong" in the input stream it should output an error message of some kind and abandon the scan. HINT: This grammar has a special property: every lexeme consists of exactly one character! Therefore this scanner will be much simpler than the one shown in 4.2 of your textbook. You may want to refer to that example, or your Week 4 recognizer solution, for ideas about how to implement this scanner