private function setRequestedAmount()
    {
        if ($this->simpleXml->{'requested-amount'}->count() < 1) {
            return;
        }

        $this->requestedAmount = new Amount(
            (float)$this->simpleXml->{'requested-amount'},
            (string)$this->simpleXml->{'requested-amount'}->attributes()->currency
        );
    }