And so if we carry out this crossing process, we get X uppercase B, x lowercase B, x uppercase B, x lowercase B. Okay? And actually we don't have to do well, yeah, let's continue, let's finish this up. So X-B-Y-X-B-Y. So from this information, what this tells us is every single individual produced in this case must carry that particular phenotype for that disease. And we know that is not consistent with the information that is given to us because these two individuals don't carry that particular phenotype as described by this pun and square.