Multiple criteria in SUMIF?

[pumpkin head]

Hi, I'm after some help regarding SUMIF.



Basically I want to add up all of the numbers in column O that have a 100 in column A, and a 6 in column D.

I can do this separately like so:

SUMIF(A:A,100,O:O)

and

SUMIF(D: D,6,O:O)

but that doesn't help me, because I want to filter out any row which doesn't have a 100 in A and a 6 in D.

Any help would be appreciated.

PH.