Freeze Dried Liver Calculator

For the raw feederz

HTML

<h2>Freeze Dried Liver Calculator</h2>

<div class="left">Daily Ounces of Food: </div>
<input type="text" id="daily_oz" />oz
<br /> 
<div class="left">% of liver intake:</div>
<input type="text" id="percent_liver" />%
<br />
<div class="left">Meat type: </div>
<select id="meat_type">
    <option value="70.8">Raw Beef Liver</option>
    <option value="76.5">Raw Chicken Liver</option>
    <option value="71.8">Raw Duck Liver</option>
    <option value="71.4">Raw Lamb Liver</option>
    <option value="71.1">Raw Pork Liver</option>
    <option value="75.5">Raw Turkey Liver</option>
    <option value="58.8">Cooked Beef Liver</option>
    <option value="66.8">Cooked Chicken Liver</option>
    <option value="58.0">Cooked Duck Liver</option>
    <option value="56.7">Cooked Lamb Liver</option>
    <option value="64.3">Cooked Pork Liver</option>
    <option value="64.0">Cooked Turkey Liver</option>
</select>
<br />
<div class="left">Moisture Content of Freeze Dried:</div> 
<input id="fd_moisture" />%
<hr />
<div class="left" style="text-align: right;">
    <input type="submit" id="btn" value="Calculate" />
</div>
<input type="text" id="result" readonly />g of freeze dried

CSS

.left {
    float: left;
    width: 250px;
}

JavaScript

var $ = document.getElementById.bind(document);

$('btn').addEventListener('click', function(){
    
    var dailyIntake = $('daily_oz').value,
        dailyLiver = dailyIntake * $('percent_liver').value / 100,
        freshSolids = 100 - $('meat_type').value,
        fdSolids = 100 - $('fd_moisture').value,
        fdRatio = freshSolids / fdSolids,
        finalOz = fdRatio * dailyLiver,
        finalG = finalOz * 28.35;
    
    $('result').value = finalG;

}, false);