Urn 1 contains 3 red and 6 blue balls, and urn 2 contains 4 red and…

Urn 1 contains 3 red and 6 blue balls, and urn 2 contains 4 red
and 3 blue balls. The urns are equally likely to be chosen.
a) If a blue ball is drawn, what is the probability that it came
from urn 1?
b) If a red ball is drawn, what is the probability that it came
from urn 2?