There're two urns. The first urn haves 2 black balls as well as 3 white balls. The second urn haves 4 black balls and 3 white balls. An urn is chosen at random, and ball is selected at the random from that urn.
a) Draw a suitable tree diagram.
b) Assign probabilities as well as conditional probabilities to the branches of the tree.
c) Calculate the probability that the ball drawn is black.