An urn contains five white and six black balls. (a) Three balls are drawn from the urn one after another without replacement, and it is found that one of them is white and the other two are black....

An urn contains five white and six black balls.

(a) Three balls are drawn from the urn one after another without

replacement, and it is found that one of them is white and the

other two are black. What is the probability that the first ball

drawn was white? What is the probability that the first ball drawn

was white if the three balls were drawn with replacement?

(b) Three balls are drawn from the urn and discarded. Then a fourth

ball is drawn from it. What is the probability that it is white?