I have three columns of data...

My Data is in Column C and Descriptions are in Column A and B.

I have a sumif function at the end of the sheet which adds Column C
based on if Column B has a given value. But whne I filter the data
using Column A, I need the sumif to give the sum only for the visible
range and not for the entire range

For example

desc type Data
r a 1
r a 1
r a 1
r a 1
s a 1
r b 2
r b 2
r b 2

=SUMIF(B2:B8,"a", C2:C8)

On filtering S in Column A I am getting only one row of data with
value of 1 and type A. That's what I want as answer. But it is giving
the answer as 5 (for the entire range)..

Which is the most effective way to do this..

Please help

Thanks in advance

Anshuman