## Question 313:

3 methods, A, B, and C are available for teaching a certain industrial skill. Only one of these methods is used in teaching a particular worker. The failure rate is 20% for A, 10% for B, and 30% for C. However, B is a more expensive and hence is used only 10% of the time, while C is very cheap and is used 50% of the time. Suppose a worker was selected at random and failed to learn the skill correctly, what is the probability that the worker was taught using method A?