passing multiple parameters to .asmx from jquery ajax GET

html

<a onclick="testGetParametersDynamic2();">fill in names and check it out</a>
<br />
<p>Enter First Name</p>
<input id="myFirstName" type="text" />
<br />
<p>Enter Last Name</p>
<input id="myLastName" type="text" />
<div id="outputGET3"></div>

c#

[WebMethod(EnableSession = true)]
[ScriptMethod(UseHttpGet = true)]
public string testGetParametersDynamic(string firstName, string lastName)
{
    string fullName = firstName + lastName;

    return fullName;
}

I have tried multiple ways of entering data bc I think this is where the problem lies

attempt 1

function testGetParametersDynamic2()
    {
        $.ajax(
        {
            post: 'GET',
            contentType: 'application/json; charset=utf-8',
            dataType: 'json',
            data: '{"firstName":"' + $('#myFirstName').val() + '","lastName":' +
                    $('#myLastName').val() + '"}',
            url: 'UtilitieService.asmx/TestGetParametersDynamic',
            success: function (result)
            {
                var test = result.d;
                var outputDiv = $('outputGET3');
                outputDiv.html(test);
            },

            error: function ()
            {
                alert('Fail Test Get Dynamic');
            }
        });
    }

attempt 2:

function testGetParametersDynamic2()
    {
        $.ajax(
        {
            post: 'GET',
            contentType: 'application/json; charset=utf-8',
            dataType: 'json',
            data: "firstName" + $('myFirstName').val() + "&lastName" + $('myLastName').val(),
            url: 'UtilitieService.asmx/TestGetParametersDynamic',
            success: function (result)
            {
                var test = result.d;
                var outputDiv = $('outputGET3');
                outputDiv.html(test);