JavaScript计算按钮不起作用

Question

此脚本不会在结尾显示计算的总计。我想不出来！有什么建议？我错过了什么？如果有帮助，我也有税务功能的JavaScript代码。一切正常，直到我到达最终计算按钮。

<H2>Business Card Pricing Calculator</H2>
<P>
    <STRONG>Type:</STRONG>
    <BR /><BR />
    <INPUT id="Horizontal" value="50" type="radio" name="type" />
    <LABEL for="Horizontal">Horizontal</LABEL> 
    <BR />
    <INPUT id="vertical" value="50" type="radio" name="type" />
    <LABEL for="vertical">Vertical</LABEL>
    <BR />
    <INPUT id="foldover" value="65" type="radio" name="type" />
    <LABEL for="foldover">Foldover</LABEL> 
</P>
<P>
    <STRONG>Options:</STRONG>
    <BR /><BR />
    <INPUT id="cutting" value="10" type="checkbox" name="cutting" /> 
    <LABEL for="cutting">Cutting</LABEL>
    <BR />
    <INPUT id="laminating" value="15" type="checkbox" name="laminating" /> 
    <LABEL for="laminating">Laminating</LABEL>
    <BR />
    <INPUT id="scoring" value="10" type="checkbox" name="scoring" /> 
    <LABEL for="scoring">Scoring</LABEL> 
</P>
<P>
    <STRONG>Tax Rate:</STRONG>
    <INPUT style="TEXT-ALIGN: right" id="tax_rate" maxLength="5" size="3" type="text"
name="tax_rate" />%
</P>
<P>
    <STRONG>Total (Including Tax): </STRONG>
    <SPAN id="total_cost"></SPAN>
</P>
<P>
    <INPUT id="calculate-button" value="CALCULATE" type="button" />
</P>

的JavaScript

$("#calculate-button").click(function () {
    var price = 0;
    var tax = 0;

    var checkedValues = $('input:checked');

    $(checkedValues).each(function (index) {
        price += parseInt(checkedValues[index].value, 10);
    });

    tax = (price * $("#tax_rate").val() / 100);

    $("#total_cost").html(price + tax);
});