Two level grouping and ranking

I have following dataset:

Year Location buyers Amount
2015 West A 12
2015 West A 14
2015 East Z 55
2015 South Y 62
2015 West O 24
2015 East B 10
2015 East B 12
2015 North B 23
2015 South K 10
2015 North C 23
2015 North M 23

Final output

if we chose top=3
West A 14
East Z 55
East Z 22
South Y 62
South K 10
North B 23
North C 23
North M 23

if top=1
West A 14
East Z 55
South Y 62
North B 23

i have to prepare a clustered bar chart that shows top n buyers for each region in terms of sum of amount they each bought (separately for each region).

but in actual there should be no gaping like this 

I have created a new measure 

Measure 10 = CALCULATE (
[Measure for summation of amount],
KEEPFILTERS (
GENERATE (
VALUES ( Table1[region]),
TOPN ( 5, ALL ( Table1[buyer] ), [Measure for summation amount] )
)
)
)