Three identical opaque urns each contain four marbles of identical size and weight. one urn contains 3 black marbles and 1 white marble. Another urn contains 3 black marbles and 1 blue marble. The third urn contains 2 black marbles, 1 blue marble, and 1 white marble. Answer the following 2 questions.
1. If you choose one of the urns at random, what is the probability that you will have chosen the urn with no blue marbles?
2. You are permitted to draw two marbles from an urn. you do so and the result is two black marbles. what is the probablity that the urn you drew from is that with no blue marbles.