WooCommerce - Hide 2nd class if free shipping is available

<?php
// WooCommerce - Hide 2nd class if free shipping is available
add_filter( 'woocommerce_package_rates', 'custom_package_rates', 100 );
function custom_package_rates( $rates ) {
  $has_free = false;
  foreach ( $rates as $rate_id => $rate ) {
    // free must be first
    if ( 'free_shipping' === $rate->method_id ) {
      $has_free = true;
    }
    if ( $has_free & '2nd Class' == $rate->label ) {
      unset( $rates[$rate_id] );
    }
  }
  return $rates;
}