Find a node in Ajax result using jQuery

My JavaScript code is making an Ajax call to retrieve a XML document and I'm having a hard time extracting a specific node from the result.

The XML returned is essentially a collection of key/value pairs and I want to extract the value for a given key. For the sake of this discussion, let's assume the returned XML looks like this:

<result>
    <keyvaluepair>
        <key>aaa</key>
        <value>1234</value>
    </keyvaluepair>
    <keyvaluepair>
        <key>bbb</key>
        <value>5678</value>
    </keyvaluepair>
</result>

and my Ajax call looks like this:

$.ajax({
    type: "POST",
    contentType: "text/xml; charset=utf-8",
    datatype: "xml",
    processData: false,
    url: "MyPage.aspx",
    success: function (data, textStatus, xhr)
    {
        var myValue = parseInt($("???", data).text());
    }
);

What would be the appropriate way to find the value associated with a given key, say "bbb"?