return totalAmountToPay.add(calculateAmountToPayForPages(certificateRequestEvent));
return totalAmountToPay.add(calculateAmountToPayForPages(certificateRequestEvent)).subtract(event.calculatePayedAmount());
    public BigDecimal calculateTotalAmountToPay(Event event, DateTime when) {        final CertificateRequestEvent certificateRequestEvent = (CertificateRequestEvent) event;        final BigDecimal totalAmountToPay = isUrgent(certificateRequestEvent) ? super                .calculateTotalAmountToPay(certificateRequestEvent, when)                .multiply(BigDecimal.valueOf(2)) : super.calculateTotalAmountToPay(event, when);        return totalAmountToPay.add(calculateAmountToPayForPages(certificateRequestEvent));    }