Horace turns up at school either late or on time. He is then either shouted at or not. The probability that he turns up late is 0.4. If he turns up late, the probability that he is shouted at is 0.7. If he turns up on time, the probability that he is still shouted at for no particular reason is 0.2.
You hear Horace being shouted at. What is the probability that he was late?
