How to show/hide an element on checkbox checked/unchecked states using jQuery?

I have this code:

   <fieldset class="question">
       <label for="coupon_question">Do you have a coupon?</label>
       <input class="coupon_question" type="checkbox" name="coupon_question" value="1" />
       <span class="item-text">Yes</span>
   </fieldset>

   <fieldset class="answer">
       <label for="coupon_field">Your coupon:</label>
       <input type="text" name="coupon_field" id="coupon_field"/>
   </fieldset>

And I would like to show/hide the "answer" fieldset (default is hidden) after a click on the checkbox in fieldset "question" How to do that. I wasn't able to do that using the technique for a classic elemetn like:

<script>
    $().ready(function(){

        $('.question').live('click',function() {
                 $('.answer').show(300);
            }
            ,
            function(){
                $('.answer').hide(200);
            }
        );

    });
</script>

Could somebody help me how to do that using checkbox? Also if possible to null (uncheck) the checkbox when it's hidden.

Attach onchange event to the checkbox:

<input class="coupon_question" type="checkbox" name="coupon_question" value="1" onchange="valueChanged()"/>

<script type="text/javascript">
    function valueChanged()
    {
        if($('.coupon_question').is(":checked"))   
            $(".answer").show();
        else
            $(".answer").hide();
    }
</script>

Try this

$(".answer").hide();
$(".coupon_question").click(function() {
    if($(this).is(":checked")) {
        $(".answer").show(300);
    } else {
        $(".answer").hide(200);
    }
});

FIDDLE