We have x uppercase by, x uppercase by. Now notice what this punning square is telling us. It tells us that 100% of the offspring that are produced, the male offspring, so this one and this one must actually exhibit that particular disease phenotype, because we have x lowercase by and x lowercase by. Now that is consistent with this individual because this individual must be x lowercase by to actually display that disease phenotype. But this individual does not display that phenotype, it is male. So that means it must be x uppercase by.