Need formula to count multiple criteria in 2 columns

[tancho321]

Hi,
I have a set of data in column A and B. I need a formula to count the occurances of given cell contents in column 1 and in column 2.
For example
Column A Column B
1c 1a
p6 p7
p5 p6
p4 p8
1b 1a
P5 1c
2c 2b

I would like the formula to count all of the occurances of P4, P5, P6 in column A and those that are still P4, P5, P6 in column B. In the case of the data above the number returned will be 3 as the P5 second bottom is not a P number in Column B. Hope that makes sense!

Any help would be gratefully received.
Thanks