If there was 40 people in a class and each had 2 balls (either black & black, white & white, black & white or white & black), you knew the colours of your 2 balls, but you didn't know the colour of anyone else's.

Based on this, how would you work out the probability of whether more than 50% of the balls in the class are black or if more than 50% of the balls are white? What would be the probability?

I was told to use Bayers' theorem, but am just not sure how I would apply it?