Set Hidden Value Depending on Selection of two Dropdowns

I am trying to set a hidden value depending on the values set for two different dropdown boxes.

Here is what I have so far, it is not working, I expect it to set the value of #bundle_option[5] to 4 when the dropdown #bundle-option-5-color is set to Black and #bundle-option-5-size is set to Child.

<script type='text/javascript'>
$j(document).ready(function() {
    $j('#bundle-option-5-color').change(function() {
        if ($j(this).find('option:selected').text() == 'Black' &&
            $j('#bundle-option-5-size').find('option:selected').text() == 'Child')
        {
        $j('#bundle_option\\[5\\]').val('4');
        }

    });
});
</script>

HTML:

<select id="bundle-option-5-color" name="bundle_option[5]" bundle-option-select="" required-entry="" required="">
<option value="">Choose a selection...</option>
<option value="Black">Black</option>
<option value="Blue">Blue</option>
<option value="Pink">Pink</option>
<option value="Purple">Purple</option>
<option value="Red">Red</option>
<option value="Teal">Teal</option>
<option value="White">White</option>
</select>

<select id="bundle-option-5-size" name="bundle_option[5]" bundle-option-select="" required-entry="" required="">
<option value="">Choose a selection...</option>
<option value="Child">Child</option>
<option value="Youth">Youth</option>
<option value="Adult Small">Adult Small</option>
<option value="Adult Medium">Adult Medium</option>
<option value="Adult Large">Adult Large</option>
<option value="Adult X-Large">Adult X-Large</option>
<option value="Adult XX-Large">Adult XX-Large</option>
</select>

<input id="bundle_option[5]" type="hidden" value="" name="bundle_option[5]">