Trying to get author’email for sending email from single.php page in wordpress?

I am trying to get author’s email in order to send a email form single.php page in WordPress. Actually I would like to get output in quotes in order to send email with wp_mail function. Right??

Here is my code for doing it all

add_action('wp_ajax_sendmail', 's3_sendmail');
add_action('wp_ajax_nopriv_sendmail', 's3_sendmail');
function s3_sendmail()
{
if(isset($_POST['submitted'])) {


if(trim($_POST['earnings']) === '') {
$earningsError = 'Please enter your earnings.';
$hasError = true;
} else {
$earnings = trim($_POST['earnings']);
}

if(trim($_POST['earnings']) === '') {
$earningsError = 'Enter an hourly rate.';
$hasError = true;
} 
else if (!preg_match("/^d+$/", trim($_POST['earnings']))) {
$earningsError = 'Please Enter a numeric value in Estimate Earnings.';
$hasError = true;
} else {
$earnings = trim($_POST['earnings']);
}

if(trim($_POST['Duration']) === '') {
$DurationError = 'Please enter duration.';
$hasError = true;
} else {
$duration = trim($_POST['Duration']);
}

//if(trim($_POST['email']) === '') {
//$emailError = 'Please enter your email address.';
//$hasError = true;
//} 
//else if (!preg_match("/^[[:alnum:]][a-z0-9_.-]*@[a-z0-9.-]+.[a-z]{2,4}$/i", trim($_POST['email']))) {
//$emailError = 'You entered an invalid email address.';
//$hasError = true;
//} else {
//$email = trim($_POST['email']);
//}

if(trim($_POST['comments']) === '') {
$commentError = 'Please enter a description.';
$hasError = true;
} else {
if(function_exists('stripslashes')) {
$comments = stripslashes(trim($_POST['comments']));
} else {
$comments = trim($_POST['comments']);
}
}



if(!isset($hasError)) {
$emailTo = get_the_author_meta( $field, $userID );
$subject = 'email subject goes here'.$name;
$body    = "Name: $Name Duration: $duration Comments: $comments ";
$headers = "Reply-To: '".$name."' <$email> rn";
if(wp_mail( $emailTo , $subject, $body, $headers ))
{
echo "<div class='success alert alert-info'>Proposal Sent<button type='button' class='close' data-dismiss='alert' aria-hidden='true'>&times;</button></div>";
}
else
{
echo "<div class='error alert alert-danger'>Mail function Error! <button type='button' class='close' data-dismiss='alert' aria-hidden='true'>&times;</button></div></div>";
}
}
else
{
$error="<div class='error'><ul>";

if($commentError!="")
{
$error=$error.'<li>'.$commentError.'</li>';
}

if($earningsError!="")
{
$error=$error.'<li>'.$earningsError.'</li>';
}

if($DurationError!="")
{
$error=$error.'<li>'.$DurationError.'</li>';
}


$error=$error."</ul>";
echo $error;
}
}
else
{
$error="<div class='error'>Error!</div>";
}
die();
}