Based on a quick examination, a computer specialist estimates that there is a 0.8 probability that a computer failure has been caused by a fault in the computer's motherboard. However, an electronic test which has a 90% probability of giving a correct indication and which can be assumed to be unbiased, indicates that the problem is not caused by the motherboard. The posterior probability that there is a fault in the motherboard is:

b.0.26

c.impossible to calculate from the information given