Hello,

...
or this:
=SUMPRODUCT((A2:A10="NA")*ISNUMBER(B2:B10)*(B2:B10 =0))
...

Funny. I thought of
=SUMPRODUCT(--(PROPER(A2:A10)="NA"),--(--(B2:B10)=0))

[Just in case of some " NA" or "NA " etc.]

Have fun,
Bernd