Sadly, there has been the crime. It has been committed by one of two suspects, which we call A and B. Before any investigation is done, we should suppose that A and B are equally likely to have committed the crime. After the investigation, it is found that guilty party had a blood type found in 10% of population. Suspect A matches this blood type. Sadly, we don't know the blood type of suspect B.
(a) Given the investigation's findings, what is the probability that suspect A is guilty?