@Override
    public void printMonthlyPayment(RenderResults renderer) {
        if (renderer != null) {
            if (fixedMonthlyPayment.equals(INITIAL_PAYMENT_AMT)) {
                calculateMortgage();
            }

            if (fixedMonthlyPayment.equals(INVALID_PAYMENT_AMT)) {
                throw new RuntimeException("Could not calculate monthly payment.");
            }

            renderer.renderMonthlyPayment(fixedMonthlyPayment);
        } else {
            throw new IllegalArgumentException("Null renderer");
        }
    }