In a certain assembly plant, three machines, B1, B2 and B3, make 30%, 45%, and 25%, respectively, of the products. It is known from past experience that 2%, 3% and 2% of the products made by each machine, respectively, are defective. Now, suppose that a finished product is randomly selected.

(1) What is the probability that it is defective?(0.0245)

(2) If a product were chosen randomly and found to be defective, what is the probability that it was made by machine B3?(0.204)