I have 2 columns as follows:

A B
-$24.00 n/a
$200 n/a
$350 n/a
$65 9.30%
$32 n/a
n/a 5%


i need a function that will count the number of times column A appears with
n/a only ( so in this case its 4). I have this so far...i don't know how to
write it so its counts the negative value:
=SUMPRODUCT(--(G5:G15=0),--(H5:H15="n/a"))

I also need a formula that will count the occurrance of when column B has a
value when column A has an n/a. In this case the answer would be 1.
I hope that make sense...