GPA Calculator - Using Select Input And Average It

My task was to build a simple GPA calculator using select input and Javascript to average it all together and return it to the user with his name. So I started with my form which looks like this

<tr><td>
<form name="GPA"
<p> Test 1</p>
</td><td>
<select id="v1">
<option value="4">A</option>
<option value="3">B</option>
<option value="2">C</option>
<option value="1">D</option>
<option value="0">F</option>
</select>
</td></tr><tr><td>

Now to the best of my knowledge that looks correct, I made sure to use integers as the values so I could average them using this function
<script type="text/javascript">
<!--
function Average(v1,v2,v3){
return Average (v1+v2+v3) / 3;
}
-->
</script>