Probability - sampling without replacement.

I have a feeling it's not as easy as I originally thought!

"There are 20 solar cells, 12 of which are flat and the rest are concentrated. If you were to pick six random cells, what is the probability you'd get three of each?"

So... 60% of all the cells are flat, meaning that the remaining 40% are concentrated and those would also be the probabilities of grabbing all six cells of the same description.

would this formula apply here: (p^x)(1-p)^(x-n)

where p is the probability, x being the description and n being the total cells?

(0.6^12)(1-0.6)^(12-20) = (0.002177) ÷ (0.000655) = 3.324 ??

A little lost, as you can surely see!

Thank you!