Sum on different number ranges and conditions

[uic46079]

I have two tables:

Tab1:

RowNumber	Cnt_From	Cnt_To	Type
1020	4000	4200	MB
1020	4300	4550	MB
1020	4650	4800	MB
1030	5000	5300	MB
1030	5380	6000	MB
2000	1020	1030	B
1040	6010	6080	MB
1040	6090	6120	MB
1050	6130	6180	MB
2100	1040	1080	B
2200	2000	2100	B

Tab2:

Cnt	Amount
4000	350
4100	300
4100	12
4250	345
5000	324
5100	554
6100	234
6120	543
6150	234

MB is the type for a Sub-group: = sum[Amount] the range in Cnt_from ... Cnt_to in Tab2[Cnt]

B is the type for a Super-group range in RowNumber: = sum the sum for each row of the RowNumbers

Result shall be:

RowNumber	Sum	Explanantion
1020	1007	sum the amount in Tab2 for Cnt in range 4000 … 4800
1030	878	sum the amount in Tab2 for Cnt in range 5000 … 6000
2000	1885	sum the sum for RowNumbers in range 1020 … 1030
1040	777	sum the amount in Tab2 for Cnt in range 6010 … 6120
1050	234	sum the amount in Tab2 for Cnt in range 6030 … 6180
2100	1011	sum the sum for RowNumbers in range 1040 … 1080
2200	2896	sum the sum for RowNumbers in range 2000 … 2100

I am looking forward for any hint how to solve this problem.... 

[Fowmy]

@uic46079 

The last line is the grand total it seems and it adds up the sub total. Do have a different Type value for grand total? 

[uic46079]

No, it´s the summarize of the row numbers 2000 up to 2100

in that case the rownumber 2000 is as well a summarized value of the rownumbers 1020 and 1030 and that is the sum of the cnt 4000 ... 4800 plus sum of the cnt 5000 ... 6000 

Means:
2000 = 1020 + 1030 = sum(4000 ... 4800) + sum(5000 ... 6000)

2100 = 1040 + 1080 = sum(6010 ... 6020) + sum(6130 ... 6180)

2200 = 2000 + 2100 = 1020 + 1030 + 1040 + 1080 = sum(4000 ... 4800) + sum(5000 ... 6000) + sum(6010 ... 6020) + sum(6130 ... 6180)