6 scavengers were analysed when flying to 20 bins in a line. The analyst found that 3 scavengers went to one bin, 2 scavengers another and 1 scavengers to a third bin. He was asked to work out the probability that this distribution occurred by chance i.e, a scavenger chooses a bin at random. (If this probability is small then it is likely that they are likely to congregate.) Explain your answer.

Well I said the $\displaystyle P(of this configuration)=_{20}C_3(\frac{1}{20})^6$. And that this probability is sufficiently low enough to be random. What do people think? Help greatly appreciated!