public static function countInvitesByClassGender($term, $class, $gender = null)
    {
        $query = "SELECT count(*) FROM hms_new_application JOIN hms_lottery_application ON hms_new_application.id = hms_lottery_application.id
                    WHERE hms_lottery_application.invited_on IS NOT NULL
                    AND hms_new_application.term = $term ";