Add Two Markers on Google Maps

<!DOCTYPE html>
<html>
  <head>
    <style>
       /* Set the size of the div element that contains the map */
      #map {
        height: 400px;
        width: 600px;
       }
    </style>
  </head>
  <body>
    <!--The div elements for the map and message -->
    <div id="map"></div>
    <div id="msg"></div>
    <script>
// Initialize and add the map
var map;
function initMap() {
  // The map, centered on Central Park
  const center = {lat: 40.774102, lng: -73.971734};
  const options = {zoom: 15, scaleControl: true, center: center};
  map = new google.maps.Map(
      document.getElementById('map'), options);
  // Locations of landmarks
  const dakota = {lat: 40.7767644, lng: -73.9761399};
  const frick = {lat: 40.771209, lng: -73.9673991};
  // The markers for The Dakota and The Frick Collection
  var mk1 = new google.maps.Marker({position: dakota, map: map});
  var mk2 = new google.maps.Marker({position: frick, map: map});
}
    </script>
    <!--Load the API from the specified URL -- remember to replace YOUR_API_KEY-->
    <script async defer
    src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap">
    </script>
  </body>
</html>