[jQuery] math with form fields

[amidude]

Okay here's my form for a BMI Calculator I'm making.

<form  action="" id="bmiCalc" onsubmit="return false;">
            <fieldset>
            <legend>Your BMI</legend>
            <ol>
                <li><label for="height">Height</label>
            <select id="feet" class="textfield">
                <option value="4">4</option>
                <option value="5">5</option>
                <option value="6">6</option>
                <option value="7">7</option>
            </select> ft
                    <select id="inches" class="textfield">
                        <option value="0">0</option>
                        <option value="1">1</option>
                        <option value="2">2</option>
                        <option value="3">3</option>
                        <option value="4">4</option>
                        <option value="5">5</option>
                        <option value="6">6</option>
                        <option value="7">7</option>
                        <option value="8">8</option>
                        <option value="9">9</option>
                        <option value="10">10</option>
                        <option value="11">11</option>
                        <option value="12">12</option>
                    </select> in</li>
                <li><label for="weight">Weight</label><input id="pounds"
type="text" class="textarea"></li>
                <li><input id="subCalc" type="image" title="submit"
alt="submit" src="imgs/btn.gif" class="submit-btn" /></li>
            </ol>
</fieldset>
</form>

My problem is that I don't know how to retreive a number value from
select items. Then the math part is pretty fuzzy too.

Here's where I am so far...am I on the right track?

$(function () {
                $('#subCalc').bind('submit',function(event) {
                        var feet = $('#feet').val();
                        var inches = $('#inches').val() || 0;
                        var pounds = $('#pounds').val();, 10);

                        var totalInches = feet * 12 + inches;
                        var bmi = Math.round(pounds * 703 * 10 / totalInches /
totalInches) / 10;
                });
  })