How much greater is the sum of the interior angles
of a rhombus than the sum of the interior angles of
a right triangle?
a 0◦
b 45◦
c 90◦
d 180◦

There are three bags: a (contains 2 white and 4 red balls), b (8 white, 4 red) and c (1 white 3 red). you select one ball at random from each bag, observe that exactly two are white, but forget which ball came from which bag. what is the probability that you selected a white ball from bag a?