In a class of `75` students, `15` are above average, `45` are average and the rest below average achievers. The probability that an above average achieving student fail is `0.005`, that an average achieving student fails is `0.05` and the probability of a below average achieving student failing is `0.15`. If a student is known to have passed, then what is the probability that he is a below average achiever?

Answer

`(170)/(939)`