SQL Group by range and total column - sql

Question

With the following function and stored procedure i get a resultset with 2 columns.
What i need additional is a third column total for all open invoices inner score range
It would great for any idea.
ALTER FUNCTION dbo.OpenOrders
(
#MandantId int
)
RETURNS TABLE
AS
RETURN
SELECT SUM(Invoices.Amount - ISNULL(Payment.Amount, 0)) AS Op
FROM Invoices INNER JOIN
Orders ON Invoices.OrderId = Orders.OrderId LEFT OUTER JOIN
Payment ON Invoices.InvoiceId = Payment.InvoiceId
WHERE (Orders.MandantId = #MandantId)
GROUP BY Invoice.InvoiceId, Invoices.Amount
HAVING (SUM(Invoices.Amount - ISNULL(Payment.Amount, 0)) <> 0)
ALTER PROCEDURE dbo.GetOpRanges
#MandantId int
AS
BEGIN
SELECT * INTO #tmp_ranges
FROM
//wrong in first post -> OPDebitorByMandant(#MandantId)
OpenOrders(#MandantId)
SELECT op AS [score range], COUNT(*) AS [number of occurences]
FROM
(SELECT CASE
WHEN op BETWEEN 0 AND 50 THEN ' 0- 50'
WHEN op BETWEEN 50 AND 100 THEN ' 50-100'
WHEN op BETWEEN 100 AND 500 THEN '100-500'
ELSE '500 and >' END AS op
FROM [#tmp_ranges]) AS t
GROUP BY op
RETURN
Result:
score range number of occurences range
------------------+-------------
0- 50 23
50-100 4
100-500 4
500 and > 21
What i need additional is a third column total for all open invoices inner score range.
Target result:
score range number of occurences Total
-----------+--------------------+------
0- 50 23 1.150
50-100 4 400
100-500 4 2.000
500 and > 21 22.000
Tables:
Invoices
InvoiceId CustomerId OrderId DateOfInvoice Amount
----------+----------+-------+-------------+------
1 1 20 20160301 1000.00
2 2 22 20160501 2000.00
3 1 102 20160601 3000.00
...
Orders
OrderId MandantId CustomerId DateOfOrder Amount
-------+---------+----------+-----------+-----------
20 1 1 20160101 1000.00
22 1 2 20160101 2000.00
102 1 1 20160101 3000.00
...
Payment
PaymentId MandantId CustomerId InvoiceId OrderId DateOfPayment Amount
---------+---------+----------+---------+-------+-------------+-------------
1 1 1 1 20 20160310 1000.00
2 1 2 2 22 20160505 2000.00
3 1 1 3 102 20160610 3000.00
...
hope it's helpfull and thanks again in advance for any solution