Three Checkboxes, One must be selected to enable submit button, needs Jquery?

Question

I have between 1-three checkboxes and by default they are all disabled. In order for the submit button to be active ove checkbox minumum must be selected. Can someone help me with a jquery snippet to achieve this? My markup looks like this and the site used jquery 1.42. Please and thankyou!

<form action="/cart/add" method="post" id="pform">
  <h3 class="goudy">Make your selection:</h3>
  <ul id="variants">
    <li>
        <input type="checkbox" name="id[]" value="39601622" id="radio_39601622" style="vertical-align: middle;" class="required" />
        <label for="radio_39601622[]">$38.00 - Original Antique Photo</label>
    </li>

    <li>
        <input type="checkbox" name="id[]" value="39601632" id="radio_39601632" style="vertical-align: middle;" class="required" />
        <label for="radio_39601632[]">$8.99 - SCAN</label>
    </li>

    <li>
        <input type="checkbox" name="id" value="39777962" id="radio_39777962" style="vertical-align: middle;" class="required" />
        <label for="radio_39777962">$2.99 - Rigid Sleeve</label>  
    </li>
  </ul>

  <div class="buttons clearfix">
    <input type="image" src="../images/add-to-cart.png" name="add" value="Add to Cart" id="add" class="send-to-cart" />
  </div>    
</form>

Answer 1

Assuming the submit button is disabled to begin with (tested):

$(document).ready(function() {

    // disable submit once the DOM is ready
    $("input.send-to-cart").attr("disabled", "disabled");
    $("input.required:checkbox").click(function() {
        $("input.send-to-cart").attr("disabled", !$("input.required:checkbox:checked").length);
    });
});

Answer 2

Try this:

$(function(){
  if ($('input[type="checkbox"]:checked').length > 0)
  {
       // submit the form now
  }
});

Answer 3

Another way:

pform = null;
numberSelected = 0;

$(function(){
    pform = $("#pform");
    $("input[type=checkbox]", pform).click({
        if ($(this).is(":selected"))
            numberSelected++;
        else
            numberSelected--;

        if (numberSelected > 0)
            $('#add').removeAttr('disabled');
        else
            $('#add').attr('disabled', true);
    });
});

Answer 4

Another way with disabled form button if nothing checked!

$(function() { 
    $('#add').attr('disabled','disabled');
    $('#pform input:checkbox').bind('click',function() {
        if($(this).is(':checked')) {
         $('#add').removeAttr('disabled');
        } else {
         $('#add').attr('disabled','disabled');
        }
   });
});​