where i am going wrong .......error i am getting  "


here is the code


<apex:page docType="html-5.0" controller="sendbusinesscard">
<apex:includeScript value="/soap/ajax/24.0/connection.js"/>
<apex:includeScript value="/soap/ajax/24.0/apex.js"/>
    <style>
    .mypage {
        font-family: "ProximaNovaSoft-Regular", Calibri;
        font-size: 110%;
        padding-top: 12px;
        width: 100%;
    }
    .mypage input[type=text] {
        width: 100%;
        height: 35px;
        -webkit-appearance: none;
        padding: 0 8px;
        margin: 4px 0;
        line-height: 21px;
        background-color: #fff;
        border: 1px solid #ddd;
        border-radius: 3px;
        outline: none;
    }
    .mypage button {
        -webkit-appearance: button;
        border-radius: 3px;
        display: block;
        padding: 12px;
        margin: 4px 0;
        width: 100%;
        background: #eee;
        border: solid 1px #ccc;
    }
</style>
    <apex:remoteObjects >
        <apex:remoteObjectModel name="User" fields="Email,FirstName,LastName,Phone,Title"/>
    </apex:remoteObjects>
    
    <div class="mypage">
        Title: <apex:outputText value="{!$User.Title}" /><br></br>
        First Name: <apex:outputText value="{!$User.FirstName}"/><br></br>
        Last Name: <apex:outputText value="{!$User.LastName}"/><br></br>
        Phone: <apex:outputText value="{!$User.Phone}" /><br></br>
        Email: <apex:outputText value="{!$User.Email}" /><br></br>
        Enter email: <input type="email" id="enteremail" /><br></br>
        <button onclick="sendemail()">Send Email</button>


    </div>
    
    <script>
        function sendemail(){
         var enteremail = document.getElementById("enteremail").value;
         console.log('1',document.getElementById("enteremail"))
         sforce.connection.sessionId = "{!$Api.Session_ID}";

        var singleRequest = new sforce.SingleEmailMessage();
        singleRequest.replyTo = "jsmith@acme.com";
        singleRequest.subject = "sent through ajax test driver";
        var fName = "{!$User.FirstName}";
                var lName = "{!$User.LastName}";
        singleRequest.plainTextBody = "this test went through ajax - "+fName+' - '+lName;
        singleRequest.toAddresses = enteremail;
        console.log('1',singleRequest)
        console.log('2'+singleRequest)
        var sendMailRes = sforce.connection.sendEmail([singleRequest]);
        //alert(sendMailRes);
        }
    </script>
    
</apex:page>

this is when i clicked check challenge

Challenge Not yet complete... here's what's wrong:
The 'BusinessCard' page isn't using the $User global variable.