** Using WeBWorK **

I'd like to provide some feedback to students when certain wrong answers are selected in multiple choice questions. As an example, for a question asking for the first nonzero even number, provide a comment if "4" is selected. The code below is modeled on the "answerhints.pl" model (in a very amateurish way) and does not work. Help?

DOCUMENT(); 

loadMacros(

  "PGstandard.pl",

  "MathObjects.pl",

  "answerHints.pl",

  "PGchoicemacros.pl"

  );

 #Multiple Choice

$radio = new_multiple_choice();

$radio->qa("What is the least nonzero even number","two");

$radio->extra("one","three","four");

$radio->makeLast("infinity"); 

 TEXT(beginproblem());

BEGIN_TEXT

 \{ $radio->print_q() \}

\{ $radio->print_a() \}

END_TEXT

 ANS(radio_cmp($radio->correct_ans())->withPostFilter(AnswerHints("four"=>"Note you want the *least* nonzero even number")));

#ANS(radio_cmp($radio->correct_ans()) ); 

ENDDOCUMENT();