protected function _replaceTenPrefixes($string)
    {
        foreach ($this->TEN_PREFIXES as $tp => $tp_replacement) {
            $string = preg_replace_callback(
                "/(?:$tp)( *\d(?=[^\d]|\$))*/i",
                function ($m) use ($tp_replacement) {
                    return $tp_replacement + (isset($m[1]) ? (int)$m[1] : 0);
                },
                $string
            );
        }
        return $string;
    }